GENERAL 
AGRICULTURAL  CHEMISTRY 


BY 


EDWIN  B.    HART 

// 

Professor  of  Agricultural  Chemistry  in  the 
University  of  Wisconsin 


AND 


WILLIAM  E.   TOTTINGHAM 

Assistant  Professor  of  Agricultural  Chemistry  in  the 
University  of  Wisconsin 


MADISON,    WISCONSIN 

1910. 


LIBRARIAN'S  FUKD 


COPYRIGHT  1910 

BY 
EDWIN  B.  HART  AND  WILLIAM  E.TOTTINGHAM. 


STATE  JOURNAL  PRINTINQ  (JOMl'AN'i 
PRINTERS  AND  STERKOTYPERS 

MADISON,  Wis. 


CONTENTS. 

i/  I    INTRODUCTION 7 

II    THE   ATMOSPHERE 23 

III  THE  SOIL 35 

IV  NATURAL  WATERS 08  > 

/¥•    THE  PLANT 7<> 

VI     FARM  MANURE Ill 

VII    COMMERCIAL  FERTILIZERS 146 

VIII    CROPS  .  : 173 

IX    THE  ANIMAL  BODY 206 

X    FEEDING  STANDARDS 229 

Xt    FOOD  REQUIREMENTS  OF  ANIMALS 248 

XII    MILK  AND  ITS  PRODUCTS 80f> 

XIII    INSECTICIDES  AND  RELATED  SUBSTANCES 294 

APPENDIX 315 

INDEX  . .                                                                            327 


218748 


PREFACE 

Since  the  time  of  Liebig,  agriculture  in  its  many  phases  has 
profited  from  the  science  of  chemistry.  A  store  of  useful  infor- 
mation has  been  made  available  through  the  study  of  the  elements 
and  compounds  fundamentally  concerned  in  the  art  of  agricul- 
ture. It  is  reasonable  to  expect  that  this  art  will  in  the  future 
be  enriched  from  the  same  source. 

This  little  book  was  written  in  the  interest  of  the  young  farmer 
and  the  student  beginning  the  study  of  agricultural  chemistry. 
No  extended  knowledge  of  chemistry  is  required  for  its  under- 
standing. It  makes  no  special  appeal  to  the  chemist.  It  is  a 
survey  of  the  general  field  of  chemistry  applied  to  agriculture, 
with  the  emphasis  always  placed  on  the  applied  side. 

Throughout  the  book  we  have  striven  to  express  safe  views 
rather  than  to  echo  the  most  recent.  Hypotheses  and  theories 
have  not  been  discussed.  We  have  attempted  to  give,  in  general, 
only  well  tested  and  established  principles.  Formulas  and  re- 
cipes have  been  avoided  as  far  as  possible.  While  we  recognize 
their  helpfulness,  nevertheless,  they  are  as  yet  but  imperfect 
expressions  of  relations  not  fully  understood. 

The  authors  have  drawn  freely  from  various  publications,  en- 
deavoring to  bring  together  from  scattered  sources  the  materials 
essential  to  such  a  work  on  agricultural  chemistry.  In  this  re- 
gard we  are  especially  indebted  to  the  works  of  Ingle,  Warington, 
Storer,  Voorhees,  Vivian,  Jordan  and  others,  all  of  which  have 
aided  greatly  in  the  preparation  of  this  work. 


CHAPTER  1. 
INTRODUCTION 

Agricultural  chemistry  concerns  itself  with  the  chemical  com- 
position of  the  food  of  plants  and  animals  and  with  the  chemical 
changes  involved  in  the  processes  of  life.  It  has  to  deal  with  the 
composition  of  soil,  air,  and  water,  of  the  bodies  of  plants  and 
animals,  of  manures  and  commercial  fertilizers  and  with  the 
chemical  changes  which  these  substances  undergo. 

Before  beginning  the  study  of  the  soil  or  air  or  the  plant  it 
will  be  necessary  for  the  student  to  learn  something  of  the  im- 
portant elements  concerned  in  agriculture  and  the  meaning  of 
some  of  the  common  terms  used  in  chemistry. 

The  whole  earth,  so  far  as  is  known,  is  made  up  of  about 
eighty-one  elements,  a  large  proportion  of  which  play  little  or 
no  part  in  the  ordinary  processes  of  plant  and  animal  life.  In- 
deed a  considerable  proportion  are  found  only  in  extremely  small 
quantities  and  are  but  curiosities  to  the  student  of  chemistry. 
From  the  standpoint  of  the  farmer  they  possess  no  interest.  They 
are  called  elements  for  the  reason  that  they  are  the  simplest  sub- 
stances known,  and  cannot  by  any  means  yet  discovered,  be  sep- 
arated into  simpler  or  different  substances.  Iron,  gold,  silver, 
zinc,  lead,  and  sulphur  are  examples  of  elements. 

The  bodies  of  plants  and  animals  are  built  up  of  compounds 
of  the  following  elements  and  these,  therefore,  become  of  the 
first  importance  to  the  farmer : 

Oxygen  Phosphorus  Sodium 

Hydrogen  Calcium  Iron 

Carbon  Magnesium  Chlorine 

Nitrogen  Potassium  Silicon 
Sulphur 

A  short  account  of  these  elements  will  be  given  at  this  place. 
Oxygen  (0)  is  the  most  abundant  and  most  important  of  the 
elements.     It  forms  about  half  the  weight  of  the  solid  crust  of 


8  Agricultural  Chemistry. 

the  earth,  eight-ninths  of  the  water,  and  about  one-fifth  of  the 
weight  of  the  air.  In  the  first  and  second  instances  the  oxygen 
is  in  a  combined  state.  That  which  is  held  in  chemical  combina- 
tion in  the  soil  takes  no  part  in  the  formation  of  plant  tissue. 
In  the  atmosphere  it  exists  as  a  free  element,  merely  mixed  with 
the  other  constituents.  Oxygen  in  the  interstices  of  the  soil  is 
an  active  agent  in  bringing  about  many  chemical  changes,  as 
oxidation  of  the  organic  matter  and  disintegration  of  the  soil 
particles.  It  also  forms  about  fifty  per  cent  of  the  compounds 
found  in  plants  and  animals. 

Oxygen  is  a  colorless,  odorless  gas  and  very  slightly  soluble  in 
water.  It  shows  great  tendency  to  combine  with  other  substances 
and  the  act  of  union  is  usually  attended  by  the  production  of 
much  heat.  Burning  or  combustion  is  nearly  always  due  to  the 
heat  produced  by  the  combination  of  the  substance  burned  with 
the  oxygen  of  the  air.  Any  substance,  which  will  burn  in  air 
(containing  about  twenty-one  per  cent  of  free  oxygen)  will  burn 
with  increased  brilliancy  in  pure  oxygen. 

It  is  possible,  with  suitable  apparatus,  to  measure  the  quantity 
of  heat  a  substance  will  produce  when  burned.  The  unit  of  heat 
here  employed  is  the  "  calorie, "  which  represents  the  quantity 
of  heat  required  to  raise  one  gram  (about  1-28  of  an  ounce)  of 
water  from  0°  to  1°  on  the  scale  of  the  centigrade  thermometer. 
A  large  Calorie,  one  thousand  times  larger  than  the  above,  is 
employed  for  the  expression  of  large  quantities  of  heat  and  will 
be  employed  here. 

When  one  gram  of  the  following  dry  substances  is  burned  in 
oxygen,  the  quantity  of  heat  produced,  expressed  in  large  Cal- 
ories, is  as  follows : 

Charcoal 8.0    Fat  of  sheep !>.4 

Hydrogen 34.4 


Wood 2.8 

Coal  7.5 

Coke 7.0 

Casein  .,  6.8 


Fat  of  butter 9.2 

Cane  sugar 4.0 

Cellulose 4.1 

Starch  .  4.1 


Introduction.  9 

In  ordinary  cases  of  burning,  the  evolution  of  heat  is  readily 
evident,  but  in  some  cases  the  combustion  is  so  slow  that  the 
heat  evolved  is  carried  away  as  fast  as  produced  and  very  slight 
or  no  elevation  of  temperature  is  apparent.  In  some  cases  of 
slow  combustion  where  the  escape  of  heat  is  hindered  from  any 
cause,  the  temperature  may  rise  so  as  to  be  perceptible  or  even 
dangerous.  It  may,  under  particularly  favorable  conditions,  rise 
sufficiently  to  start  a  rapid  combustion  with  oxygen  and  flames 
then  result.  Such  cases  of  "spontaneous  combustion"  frequently 
occur.  Drying  oils,  as  linseed  or  cotton-seed  oil,  especially  when 
spread  on  cotton  waste,  and  fermentation  changes  in  vegetable 
matter  as  hay  and  tobacco  are  notable  examples  of  these  condi- 
tions. 

Hydrogen  (II).  This  element  is  rarely  found  in  a  free  state 
in  nature,  but  is  combined  with  carbon  and  oxygen  as  in  animal 
and  vegetable  matter,  with  oxygen  to  form  water,  and  in  a  few 
cases  with  some  of  the  base  elements  to  form  hydroxides.  It  is 
not  found  in  large  amounts  in  the  soil  and  that  which  forms  a 
part  of  the  tissues  of  plants  and  animals  comes  largely  from  the 
hydrogen  in  water.  It  is  a  colorless,  odorless  gas  and  charac- 
terized by  its  lightness.  This  fact  has  led  to  its  use  for  filling 
balloons,  although  coal  gas  is  now  more  generally  employed  but 
is  not  nearly  so  efficient.  In  a  free  state  it  has  been  found  in 
the  gases  escaping  from  volcanoes. 

Carbon  (C)  is  the  element  most  closely  associated  with  plant 
and  animal  life.  It  forms  a  large  proportion  of  the  solid  matter 
of  all  living  beings;  and  the  chemical  processes  of  animal  and 
plant  life  are  mainly  those  in  which  carbon  plays  an  important 
part.  It  exists  in  the  combined  state  in  many  minerals  as  the 
carbonates  of  calcium,  magnesium,  iron,  zinc,  and  also  in  a  small 
but  very  important  constituent  of  the  air,  carbon  dioxide.  The 
carbon  of  the  soil,  where  it  exists  as  the  main  constituent  of 
organic  bodies,  takes  no  direct  part  in  forming  the  carbon  com- 
pounds of  the  plant.  It  is  not  necessary  to  apply  carbon  fer- 


10  Agricultural  Chemistry. 

tilizers  to  produce  the  carbon  compounds  of  the  plant,  because 
the  carbon  dioxide  of  the  air  is  the  source  for  crop  production. 
It  is  estimated  that  there  are  about  thirty  tons  of  carbon  dioxide 
in  the  air  over  every  acre  of  the  earth's  surface. 

This  element  occurs  in  three  distinct  forms:  (1)  as  the 
diamond,  (2)  as  graphite  and  (3)  as  charcoal,  lamp  black,  etc. 
The  diamond  is  crystalline  and  transparent ;  graphite  is  crystal- 
line but  opaque ;  while  lamp  black  and  charcoal  are  non-crystal- 
line. The  black  carbon  which  is  produced  when  animal  or  vege- 
table substances  are  strongly  heated  without  access  of  air  (char- 
ring) is  due  to  the  separation  of  free  carbon  from  the  various  car- 
bonaceous compounds  present. 

Nitrogen  (N)  is  much  less  abundant  in  nature  than  the  ele- 
ments already  described.  A  peculiarity  of  its  occurrence  is  that 
it  appears  to  be  present  only  in  the  outermost  portion  of  the  earth, 
the  greater  portion  being  free  in  the  air.  No  true  minerals  con- 
taining it  are  known  except  those  which  owe  their  origin  directly 
to  plant  or  animal  life,  as  coal,  and  Chili  salt-petre.  All  living 
matter,  however,  contains  it  as  an  essential  constituent.  In  its 
free  state  it  is  a  colorless,  odorless  gas,  showing  little  tendency  to 
combine  with  other  elements.  It  constitutes  about  seventy-nine 
per  cent  of  the  atmosphere  and  over  each  acre  of  land  there  is 
consequently  about  thirty  thousand  tons. 

Although  in  the  free  state  it  is  so  inert,  the  nitrogen  compounds, 
as  a  rule,  possess  great  chemical  activity  and  many  are  very  im- 
portant substances.  Some  powerful  drugs  and  poisons  as  quin- 
ine, strychnine,  and  prussic  acid  contain  nitrogen,  while  most  ex- 
plosives, as  nitro-glycerine  and  gun  cotton  are  also  nitrogen  com- 
pounds. It  is  an  absolutely  essential  ingredient  in  the  food  of 
both  animals  and  plants.  It  must  be  supplied  to  animals  in  com- 
pounds in  which  it  is  combined  with  carbon,  hydrogen,  oxygen, 
and  certain  other  elements  and  which  are  known  as  proteins, 
while  plants  acquire  it  generally  from  nitrates,  which  are  simple 
compounds  of  oxygen,  nitrogen,  and  some  base,  as  calcium,  so- 
idum,  and  potassium.  Only  under  very  special  conditions  can 


Introduction.  11 

some  species  of  plants  obtain  their  necessary  nitrogen  from  the 
air.  It  will  be  seen  in  the  later  chapters  that,  although  plants 
are  surrounded  by  air,  rich  in  free  nitrogen,  combined  nitrogen 
is  one  of  the  essential  and  most  valuable  constituents  of  manures. 
A  large  part  of  the  nitrogen  in  the  food  consumed  by  man  and 
animals  is  eliminated  as  simple  compounds  in  the  excreta  and  un- 
fortunately, especially  in  our  cities,  sent  down  the  sewers  and 
rivers  and  finally  discharged  into  the  sea.  To  agriculture  this 
valuable  combined  nitrogen  is  therefore  wasted.  This  element  is 
the  most  expensive  of  those  necessary  for  plant  growth  and  is 
among  those  liable  to  be  most  deficient  in  our  soils.  No  other  ele- 
ment takes  such  an  important  part  in  agriculture  or  in  life  pro- 
cesses. 

Sulphur  (S)  is  found  both  free  and  combined  in  nature.  The 
free  element  is  found  in  volcanic  districts,  while  in  the  combined 
state  it  occurs  as  hydrogen  sulphide  in  mineral  waters  and  as  sul- 
phides of  many  metals,  as  for  example  iron,  lead,  and  zinc.  The 
sulphide  of  iron,  known  as  iron  pyrites,  is  often  mistaken  for  gold 
because  of  its  yellow  color ;  sulphur  also  occurs  as  sulphate  of  cal- 
cium, in  which  form  it  is  very  widely  distributed  in  soils,  and  is 
the  main  source  of  the  sulphur  for  crops. 

The  element  sulphur  (brimstone)  is  a  yellow,  brittle  substance 
and  very  inflammable.  It  burns  in  air  with  a  pale  blue  flaflBi 
forming  the  suffocating  gas,  sulphur  dioxide.  Such  forms  of  sul- 
phur are  very  poisonous  to  plants  and  animals,  while  sulphates 
are  not  only  harmless,  but  necessary.  Sulphur  is  presenlj  in  the 
proteins  of  both  plants  and  animals  and  when  putrefaction  of 
these  substances  occurs  is  often  liberated  as  hydrogen  sulphide. 
This  substance  is  perceptible  by  its  disagreeable  odor  as  one  of 
the  chief  products  of  the  decay  of  eggs. 

There  is  generally  less  than  0.10  per  cent  of  sulphur  trioxide. 
as  sulphates  in  ordinary  soil,  and  it  is  now  known  that  the  amount 
required  by  crops  is  considerable ;  for  this  reason  it  may  be  neces- 
sary to  use  certain  sulphates  occasionally  as  fertilizers  and  as 
sources  of  sulphur  for  the  growing  crops. 


12  Agricultural  Chemistry. 

Phosphorus  (P)  always  occurs  in  a  state  of  combination. 
Phosphorus  compounds,  chiefly  phosphates,  are  very  widely  dis- 
tributed, but  in  small  proportion,  in  the  rocks  of  the  earth.  De- 
posits of  calcium  phosphate  occur  in  certain  localities  and  are 
one  of  the  chief  sources  of  our  phosphate  fertilizers.  All  fertile 
soils  contain  small  quantities  of  phosphates,  which  are  taken  up 
by  plants  and  through  plants  find  their  way  into  animals,  where 
they  accumulate  in  the  bones  or  other  hard  parts,  as  teeth  and 
shells. 

The  element  phosphorus,  as  usually  prepared,  is  a  yellowish 
waxy  substance,  which  has  the  power  of  emitting  a  faint  light 
when  exposed  to  the  air.  This  property  was  the  origin  of  its 
name,  which  is  derived  from  the  Greek  and  means  "the  light 
bearer. "  The  emission  of  light  is  due  to  slow  combination  with 
the  oxygen  of  the  air,  resulting  in  the  production  of  heat. 

Phosphorus  is  a  violent  poison.  It  is  largely  used  in  the  man- 
ufacture of  lucifer  matches  and  rat-poison.  For  the  farmer  its 
chief  importance  lies  in  the  use  of  its  compounds,  the  phosphates, 
as  fertilizers,  and  its  occurrence  in  certain  fats  and  protein  com- 
pounds of  feeding  stuffs  and  in  the  bodies  of  animals. 

Soils  are  quite  liable  to  be  deficient  in  phosphates,  as  the  latter 
are  largely  drawn  upon  by  many  crops,  particularly  grain  crops, 
4^re  the  phosphorus  accumulates  in  the  seed  and  is  sold  from 
the  farm. 

Calcium  (Ca)  is  very  abundant  in  nature,  always  occurring  in 
a  combined  state.  Calcium  carbonate  is  found  in  enormous  quan- 
tities, as  chalk,  limestone  and  marble,  and  contains  the  three  ele- 
ments, calcium,  carbon  and  oxygen.  It  also  occurs  as  gypsum,  a 
compound  of  calcium,  sulphur  and  oxygen.  The  element  itself 
is  an  easily  oxidisable  metal,  difficult  to  prepare,  and  of  no  im- 
portance to  the  farmer.  Its  oxide,  or  a  compound  of  calcium  and 
oxygen,  is  the  important  substance,  quick  lime.  This  is  made  by 
burning  limestone,  whereby  the  carbon  and  part  of  the  oxygen 
are  removed  as  a  gas.  Calcium  is  an  essential  constituent  of 


Introduction.  13 

plant  food  and  in  the  soil  is  present  in  a  variety  of  forms,  as 
calcium  carbonate,  calcium  sulphate  and  calcium  phosphate. 

Potassium  (K)  occurs  in  many  minerals.  It  will  be  found  in 
many  silicates,  as  orthoclase  or  mica,  which  are  complex  com- 
pounds of  potassium,  silicon,  aluminum,  oxygen  and  other  ele- 
ments. It  also  occurs  in  sea  water,  from  which  sea  weeds  accu- 
mulate large  quantities  of  potassium  compounds.  The  immense 
salt  deposits  at  Stassfurth,  Germany,  furnish  a  large  proportion 
of  the  potassium  used  in  our  potash  fertilizers. 

The  element  is  a  lustrous  metal,  very  soft,  and  so  susceptible  to 
change  in  the  air  that  it  must  be  kept  away  from  contact  with 
air  or  moisture  by  immersion  in  naphtha.  By  contact  with  water 
it  reacts  violently,  producing  much  heat  and  floating  on  the  sur- 
face of  the  water  with  a  hissing  sound. 

Potassium  compounds  are  of  the  greatest  importance  in  agri- 
culture and  are  necessary  constituents  of  all  fertile  soils.  They 
are  intimately  associated  with  the  growth  and  increase  of  plants 
and  are  always  found  in  greatest  abundance  in  the  twigs,  young 
leaves  and  other  rapidly  growing  portions.  In  some  plants  the 
potassium  is  in  combination  with  certain  organic  acids,  as  citric 
and  tartaric  acids.  In  the  ash  of  plants — that  which  is  left  after 
burning — it  generally  occurs  as  a  carbonate.  Potassium  salts  are 
very  soluble  in  water,  but  are  absorbed  and  retained  by  certain 
constituents  of  the  soil,  so  that  their  loss  by  drainage  from  soil 
is  little  to  be  feared. 

Sodium  (Na)  is  very  widely  distributed  in  nature  and  is  a  con- 
stituent of  many  silicates.  In  the  form  of  sodium  chloride — a 
compound  of  sodium  and  chlorine — it  is  very  plentiful  as  rock 
salt  and  as  the  largest  saline  constituent  of  sea-water. 

Its  properties  resemble  those  of  potassium.  Sodium  compounds 
are  largely  used  in  the  arts  and  the  preparation  of  sodium  car- 
bonate is  one  of  the  largest  and  most  important  of  chemical  in- 
dustries. 

Sodium  is  found  in  the  ash  of  most  plants,  but,  except  in  the 


14  Agricultural  Chemistry. 

case  of  certain  plants,  does  not  appear  to  be  essential  to  their 
development.  A  striking  difference  between  sodium  and  potas- 
sium compounds,  which  are  so  much  alike  in  most  of  their  proper- 
ties, is  in  their  behavior  towards  the  soil  when  applied  in  solution. 
The  potassium  salts  are  retained  by  the  clay  and  organic  matter 
in  an  insoluble  form,  but  the  sodium  salts  are  more  easily  washed 
out  by  water  and  escape  into  the  drains.  Although  like  potassium 
in  its  chemical  properties  it  cannot  take  its  place  in  agriculture. 

Magnesium  (Mg)  is  widely  met  in  nature  as  carbonate  and 
silicate.  The  element  itself  is  a  bright,  silvery  metal,  and  capable 
of  burning  in  air  with  an  intense  and  dazzling  white  light.  Mag- 
nesium is  found  in  the  ash  of  plants  and  is  required  by  all  crops. 
It  is  particularly  abundant  in  the  seeds.  There  is  generally  in 
all  soils  an  amount  sufficient  for  crop  purposes  and  it  is  not 
necessary  to  consider  this  element  in  connection  with  fertilizers. 

Iron  (Fe)  occurs  in  a  large  number  of  compounds.  Haematite, 
a  compound  of  iron  and  oxygen,  magnetite,  a  similar  com- 
pound, but  with  a  different  proportion  of  oxygen,  and  spathic 
iron  ore,  a  compound  of  iron,  carbon,  and  oxygen ;  the  above  are 
all  abundant  minerals  and  valued  as  ores  of  iron.  The  element 
occurs  in  two  states  of  combination  with  oxygen,  one  a  relatively 
small  amount  and  called  ferrous  iron,  the  other  a  relatively  larger 
amount  and  designated  ferric  iron.  The  former  yields  salts  which 
are  white  or  green  in  color,  while  those  of  the  latter  are  red  or 
yellow.  Ferrous  compounds  are  often  present  in  rocks  or  min- 
erals deep  under  ground,  but  when  brought  to  the  surface  they 
combine  with  the  oxygen  of  the  air  to  form  ferric  compounds. 
The  change  of  the  state  of  iron  is  indicated  by  a  change  in  color, 
often  from  green  or  gray  to  red  or  yellow.  Only  ferric  com- 
pounds should  exist  in  good  soils.  Iron  is  essential  to  plants,  but 
a  small  quantity  is  all  that  is  required  and  most  soils  contain 
from  one  to  four  per  cent,  an  abundant  supply. 

Chlorine  (Cl)  is  very  abundant,  especially  in  combination  with 
sodium,  as  rock  salt  in  the  sea  and  in  spring  water.  Other  com- 
pounds of  chlorine  also  occur  as  minerals.  The  element  chlorine 


Introduction.  15 

is  a  yellowish  green  gas  with  an  irritating  and  suffocating  smell, 
very  soluble  in  water  and  of  great  chemical  activity.  The  prop- 
erties of  chlorine,  which  are  most  valued  in  the  arts,  are  its 
bleaching,  disinfecting  and  deodorizing  powers.  It  readily  de- 
stroys most  coloring  matters  and  is  largely  employed  in  bleaching 
vegetable  textile  fabrics,  as  cotton  or  linen.  It  cannot  be  used  for 
woolen  or  silk  fabrics,  as  it  injures  the  fibres  themselves.  Chlor- 
ine only  bleaches  in  the  presence  of  water  and  it  really  acts  by 
decomposing  the  water,  with  formation  of  oxygen,  which  is  the 
active  agent.  Its  action  as  a  disinfectant  is  probably  due  to  the 
same  process,  the  oxygen  of  the  water  combining  with  the  or- 
ganic matter  and  micro-organisms  and  destroying  them. 

Chlorine  is  present  in  all  soils,  generally  in  combination  with 
sodium,  as  sodium  chloride.  It  is  present  in  all  plants,  although 
its  necessity  for  plant  growth  may  be  questioned.  Crops  have 
been  brought  to  maturity  in  its  entire  absence.  Chlorine  with 
sodium,  as  common  salt,  is  sometimes  used  as  an  indirect  fertilzer. 

Silicon  (Si)  is  extremely  abundant  in  the  rocks  of  the  earth's 
crust,  and  though  it  forms  a  very  important  ingredient  in  soils 
and  occurs  in  most  plant  ashes,  it  does  not  appear  to  be  abso- 
lutely essential  as  a  plant  food.  Some  recent  work,  however,  has 
shown  that  soluble  silica  in  a  soil  enables  a  plant  to  subsist  in  the 
presence  of  a  smaller  quantity  of  phosphoric  acid  than  would  be 
necessary  without  the  silica. 

The  element  itself  is  a  brown  solid  and  at  one  time  was  difficult 
to  prepare  in  any  quantity.  At  present,  with  the  electric  fur- 
nace, it  is  easily  produced  and  its  price  per  pound  has  been 
greatly  reduced. 

The  oxide,  called  silica,  is  a  compound  of  silicon  and  oxygen 
and  is  a  very  abundant  substance,  occurring  free  as  quartz,  flint 
and  sand ;  in  combination  with  metals  the  very  numerous  and  im- 
portant substances  called  silicates,  are  produced.  It  has  been 
estimated  that  nearly  half  of  the  solid  mass  of  the  earth's  crust 
consists  of  silica. 


]  0  .1  fir ir nil ural  Ohemistry. 

DEFINITIONS. 

It  now  becomes  necessary  to  define,  in  a  fragmentary  way, 
some  of  the  commoner  terms  used  in  chemistry. 

Acid.  A  substance  generally  possessing  a  sour  taste  and  the 
property  of  changing  vegetable  blues,  as  blue  litmus,  to  red.  As 
types  of  acids,  we  have  sulphuric  acid,  commonly  used  for  the 
Babcock  test,  and  acetic  acid,  the  principal  acid  in  vinegar.  The 
possession  of  a  sour  taste  and  the  power  of  changing  vegetable 
blues  to  red  is  indicated  by  saying  that  the  substance  has  an  acid 
reaction. 

Alkali.  A  substance  opposed  in  its  properties  to  an  acid,  cap- 
able of  neutralizing  and  destroying  the  characteristics  of  an  acid, 
forming  in  so  doing,  a  salt.  The  most  important  alkalies  are 
soda,  potash,  lime,  and  ammonia.  A  substance  is  said  to  have  an 
alkaline  reaction  if  it  turns  certain  vegetable  colors,  as  red  litmus, 
to  a  blue  color. 

Organic  matter,  strictly  speaking,  is  matter  which  has  been 
produced  by  organisms,  such  as  plants  or  animals,  but  the  term 
is  used  in  a  wider  sense  in  chemistry  for  any  compound  of  carbon, 
whether  produced  by  life  processes  or  artificially.  Almost  all 
forms  of  organic  matter,  when  strongly  heated  out  of  contact  with 
air,  blacken,  owing  to  the  liberation  of  carbon.  With  free  access 
of  air,  combustion  occurs,  and  carbon  dioxide  and  other  products 
are  formed. 

Oxidation  and  Reduction.  By  oxidation,  literally  speaking, 
is  meant  union  with  oxygen,  but  in  a  chemical  sense  the  term  is 
given  a  wider  significance,  that  is,  combination  with  more  oxygen 
or  with  some  substance  playing  the  part  of  oxygen. 

Reduction  is  used  in  exactly  the  opposite  sense.  A  substance 
,  which  brings  about  oxidation,  is  called  an  " oxidizing  agent" 
while  one  which  removes  oxygen  is  called  a  "reducing  agent." 
Common  oxidizing  agents  are  air,  nitric  acid,  nitrates  and  chlor- 
ine ;  common  reducing  agents  are  easily  oxidizable  metals,  as  zinc, 
and  n mi iy  forms  of  decaying  organic  matter. 


Introduction.  17 

Fermentation.  A  process  of  decomposition,  often  accompan- 
ied by  the  oxidation  of  carbonaceous  matter,  and  produced  by  the 
life  processes  of  bacteria,  yeasts  and  molds.  When  the  process 
occurs  out  of  free  access  of  air  and  bad  smelling  gases  are  formed, 
the  process  is  called  putrefaction. 

The  constituents  of  plants.  All  agriculture  depends  upon  the 
growth  of  plants  and  consequently  all  profit  for  the  farmer  de- 
pends upon  the  value  of  the  crop  his  farm  produces.  This  is 
true  whether  the  crop  is  sold  directly  from  the  farm  or  whether 
it  is  fed  to  animals  and  the  products  such  as  live  stock,  beef,  pork, 
wool,  eggs,  or  milk,  used  as  the  source  of  revenue.  If  the  crops 
now  produced  on  two  hundred  acres  of  land  could  be  grown  on 
one  hundred  without  a  great  increase  of  labor  and  other  expense, 
the  profit  would  be  greater.  Successful  farmers  have  demon- 
strated that  the  present  average  of  crops  can  be  doubled,  and  that 
at  a  cost  per  acre  scarcely  more  than  is  now  required  for  the  one- 
half  crop. 

To  accomplish  this  requires  a  broader  knowledge  of  the  food 
requirements  of  plants  than  is  possessed  by  most  of  our  farmers. 
A  thorough  understanding  of  the  subject  of  plant  food  and  plant 
nutrition  by  our  forerunners  in  agriculture  would  have  rendered 
it  unnecessary  to  emphasize  constantly  the  relation  of  the  con- 
stituents of  the  plant  to  soil  exhaustion. 

It  is  common  experience  that  continued  cropping  results  in  a 
loss  of  fertility.  The  productiveness  of  a  virgin  soil  seems  un- 
limited, for  large  crops  are  produced  from  year  to  year  with  no 
apparent  decrease.  But  sooner  or  later  they  begin  to  diminish 
in  size,  gradually  to  be  sure,  but  unceasingly,  until  at  last  the 
yield  becomes  so  small  as  to  make  the  cost  and  labor  of  produc- 
tion unprofitable. 

At  the  Experiment  Station  at  Rothamsted,  England,  barley 
grown  continuously  on  the  same  plot  for  forty-three  years  with- 
out the  use  of  fertilizers  of  any  kind,  yielded  in  the  forty-third 
year  10  bushels  of  dressed  grain  per  acre,  the  average  for  the 
last  eight  years  being  1134  bushels.  Wheat  grown  for  fifty  years 


18  Agricultural  Chemistry. 

in  the  same  way  produced  in  the  fiftieth  year  9%  bushels  of  grain 
per  acre,  the  average  for  the  last  eight  years  being  111/2  bushels. 
The  soil  seems  capable  of  keeping  up  the  yield  indefinitely,  but 
the  amount  of  crop  produced  ceases  to  be  profitable. 

It  is  evident  that  the  virgin  soil  must  have  contained  large 
amounts  of  some  substances  that  were  necessary  for  vigorous 
plant  growth  arid  that  these  were  removed  by  the  successive  crops 
when  harvested.  The  rapid  decrease  in  fertility  finds  its  most 
rational  explanation  on  this  basis.  Changes  in  climate  and  phy- 
sical condition  of  the  soil  are  inadequate  as  explanations  for  this 
decreased  productive  power. 

A  description  of  the  elements  important  to  agriculture  has  al- 
ready been  given  and  the  very  reason  for  their  importance  to  the 
farmer  lies  in  the  fact  that  they  are  the  elements  which  constitute 
the  compounds  of  plants  and  are  removed  from  the  soil  when  the 
crop  is  harvested. 

Source  of  elements.  However,  not  all  of  the  elements  de- 
scribed have  come  from  the  soil.  Plants  obtain  the  elements  of 
which  they  are  built  up  partly  from  the  soil  and  partly  from  the 
atmosphere.  From  the  soil  they  obtain  by  means  of  their  roots 
all  their  ash  constituents,  all  their  sulphur  and  phosphorus,  and 
in  most  cases,  nearly  the  whole  of  their  nitrogen  and  water.  From 
the  atmosphere  they  obtain,  through  the  instrumentality  of  their 
leaves,  the  whole  or  nearly  the  whole,  of  their  carbon.  There  are 
exceptions,  especially  in  regard  to  nitrogen,  which  is  obtained 
from  the  atmosphere  by  certain  plants,  such  as  alfalfa,  clover, 
vetch,  pea  and  bean,  under  certain  conditions  to  be  described 
later. 

Composition  of  the  plant.  The  most  abundant  ingredient  of 
a  living  plant  is  water.  Many  succulent  vegetables,  as  the  turnip 
and  lettuce  contain  more  than  ninety  per  cent  of  water.  The 
green  corn  plant  contains  eighty-five  to  ninety  per  cent  of  water. 

Combustible  part  of  plants.  If  a  stalk  of  corn  is  dried  and 
burned  the  greater  part  is  consumed  and  passes  away  in  the  form 
of  gas.  But  there  is  always  left  behind  a  small  quantity  of  white 


Introduction.  19 

ash,  corresponding  exactly  to  the  ash  left  in  the  stove  after  a  stick 
of  timber  is  burned. 

The  constituents  which  form  the  dry  matter  of  plants  may  be 
divided  into  two  classes — the  combustible  and  the  non-combustible 
part.  The  combustible  part  of  plants  is  made  up  of  six  chemical 
elements — carbon,  oxygen,  hydrogen,  nitrogen  and  sulphur,  with 
a  small  amount  of  phosphorus.  Without  these  no  plant  will  grow. 
Carbon  generally  forms  about  one-half  of  the  dry  combustible 
part  of  plants.  Nitrogen  seldom  exceeds  four  per  cent  of  the  dry 
matter  and  is  generally  present  in  much  smaller  amounts.  Sul- 
phur and  phosphorus  are  still  smaller  in  quantity.  The  re- 
mainder is  made  up  of  oxygen  and  hydrogen.  The  carbon,  hy- 
drogen and  oxygen  form  the  cellulose,  starch,  lignin,  gummy  mat- 
ters, sugars,  fats  and  vegetable  acids  which  plants  contain.  The 
same  elements  united  with  sulphur  and  nitrogen  form  the  very 
important  proteins,  which  are  the  life  centers  of  the  plant.  When 
all  the  above  elements  are  united  to  phosphorus,  we  have  addi- 
tional important  groups  of  plant  compounds,  called  nucleins  and 
lecithins. 

Non-combustible  part  of  plants.  The  non-combustible  or  ash 
constituents  form  generally  but  a  small  part  of  the  plant.  A 
fresh,  mature  corn  plant  will  contain  about  1.2  per  cent  of  ash, 
while  the  corn  grain  when  dry,  contains  about  1.5  per  cent.  In 
the  straw  of  cereals  the  ash  constitutes  4-7  per  cent  and  cereal 
grains  2-3  per  cent  of  the  dry  matter.  In  hay  5-9  per  cent  will 
be  found.  We  find  in  leaves,  especially  old  leaves,  the  greatest 
proportion  of  ash.  In  the  leaves  of  root  crops  the  ash  will  amount 
to  10-25  per  cent  of  the  dry  matter. 

Essential  elements.  The  non-combustible  ash  always  contains 
six  elements — potassium,  magnesium,  calcium,  iron,  phosphorus 
and  sulphur.  It  was  once  thought  that  these  ash  elements  were 
accidental,  simply  dissolved  in  the  soil  water  and  absorbed  by  the 
plant  and  that  they  were  not  essential  to  its  development.  Liebig 
proved  that  they  were  necessary;  seeds  were  planted  in  pure 
quartz  sand  contained  in  a  series  of  pots  to  one  of  which  nitrogen 


20 


Agricultural  Chemistry. 


compounds  alone  were  added,  and  to  the  others,  nitrogen  com- 
pounds plus  a  small  amount  of  plant  ash.  The  plants  in  the  pots 
which  received  the  ash  grew  to  maturity,  while  those  in  the  other 
pots  made  only  a  feeble  growth. 


Water  cultures  of  buckwheat.     This  method  of  experimental  culture, 
which  is  known  as  water  culture,  has  been  of  the  greatest  service 
in  determining  which  elements  are  essential  for  plant  growth. 
No.  1.    Plant  grown  in  normal  solution. 

Plant  grown  in  normal  solution  without  potassium. 
Plant  grown  in  normal  solution  with  sodium  instead  of 

potassium. 

Plant  grown  in  normal  solution  without  calcium. 
Plant  grown  in  normal  solution  without  nitrogen. 


No.  2. 
No.  3. 

No.  4. 
No.  5. 


Non-essential  elements.  Besides  the  elements  just  named  an 
ash  will  generally  contain  sodium,  silicon,  chlorine,  and  frequent- 
ly manganese,  and  perhaps  minute  traces  of  other  elements. 
These  elements  just  named  sometimes  form  a  considerable  portion 


Introduction.  21 

of  the  ash.  For  the  reason  that  plants  have  been  brought  to 
maturity  in  their  absence,  it  has  been  generally  accepted  that  they 
are  non-essential.  However,  it  is  necessary  to  remember  that 
such  experiments  have  generally  extended  over  a  single  genera- 
tion and  that  it  is  possible  that  an  attempt  to  grow  the  crop 
through  successive  generations  from  its  own  seed  in  a  soil  devoid 
of  sodium,  chlorine,  silica,  or  manganese  might  meet  with  failure. 

How  ash  elements  occur.  The  ash  elements  named  above  oc- 
cur in  part  in  the  plant  as  salts,  being  combined  with  phosphoric, 
nitric,  sulphuric  and  various  vegetable  acids  of  which  acetic, 
oxalic,  malic,  tartar ic  and  citric  acids  are  the  most  common.  It 
is  also  very  certain  that  part  is  in  combination  with  the  organic 
or  combustible  part  of  the  plant.  Sulphur  occurs  partly  as  sul- 
phates and  also  as  a  constituent  of  proteins.  Phosphorus  as  a 
phosphate  in  the  stem  and  root  of  the  plant,  but  in  organic  form 
in  its  seeds.  In  addition,  such  ash  elements  as  potassium,  mag- 
nesium, calcium,  iron  and  silicon  are  very  probably  in  part  con- 
stituents of  the  organic  compounds  of  plants. 

It  is  usual  to  speak  of  the  combustible  ingredients  of  a  plant 
as  organic,  and  of  the  non-combustible  ingredients  as  inorganic. 
This  is  not  accurate,  as  these  ash  constituents,  which  are  essential 
for  the  growth  of  the  plant,  have  during  its  life  as  much  right 
to  be  called  organic  as  the  carbon  of  starch  or  protein. 

Can  one  element  displace  another?  The  fact  that  some  of  the 
elements  found  in  plant  ash,  as  sodium  and  potassium,  are  chem- 
ically very  much  alike,  has  led  to  the  attempt  to  displace  the  ex- 
pensive and  less  commonly  occurring  potassium  by  the  inexpen- 
sive and  relatively  abundant  element,  sodium.  If  it  were  pos- 
sible to  do  this,  the  farmer's  fertilizer  bills  for  potassium  salts 
would  be  materially  reduced.  However,  experiments  have  dem- 
onstrated that  sodium  cannot  take  the  place  of  potassium  in  the 
growth  of  the  plant. 

A  definite  amount  of  all  the  essential  elements  is  needed  for  <\ 
certain  yield  and  none  of  the  elements  can  be  replaced  by  another. 
A  crop  will  be  limited  by  the  quantity  of  the  essential  element 


22 


A gric it Uural  Cli emistry. 


present  in  least  quantity  compared  with  the  requirements  of  that 
crop.  If  a  field  of  corn  can  obtain  only  potash  enough  for  a  half 
crop,  no  more  than  this  can  be  produced,  no  matter  how  much  of 
the  other  forms  of  plant  food  is  present. 

The  following  table  shows  the  ingredients,  expressed  as  pounds, 
in  1000  Ibs.  of  the  matured  corn  plant,  when  the  plant  is  to  be 
cut  for  shocking : 


Corn  Plant 
1000  Ibs. 


Water 
793 


( Hydrogen 
(  Oxygen . . . 


704.9 


f  Organic  matter 
195 


f  Nitrogen 2.9 

!  Carbon  . .       . .  90.5 


Oxygen.. 88.1 

Hydrogen 12.' 


Dry  matter  - 

207 


Ash  12 


f  Protein 18 

j  Fat 5 

|  Fibre 50 

[  Carbohydrates  . .  122 

f  Chlorine  0.4 

Potash 4.0 

Phosphoric  acid.  1.2 

Lime ...  1.6 

Magnesia 1.4 

Iron  oxide 0.3 

Sulphur  trioxide.  0.3 

Soda 0.4 

Silica 2.4 

All  the  elements  mentioned  above  as  occurring  in  the  ash,  with 
the  exception  of  chlorine,  are  combined  with  oxygen.  In  the 
table  the  names  under  '  *  ash ' '  represent  these  combinations :  pot- 
ash is  composed  of  potassium  and  oxygen;  phosphoric  acid  of 
phosphorus  and  oxygen;  lime  of  calcium  and  oxygen;  sulphur 
trioxide  of  sulphur  and  oxygen. 

The  table  shows  that  three  elements,  hydrogen,  oxygen  and  car- 
bon, make  up  98%  per  cent  of  the  entire  composition  of  the  plant, 
the  remaining  elements  constituting  only  1%  per  cent. 


CHAPTER  II 
THE  ATMOSPHERE 

The  atmosphere  or  air  forms  an  invisible  envelope  surrounding 
and  resting  upon  the  earth.  It's  exact  thickness  is  unknown,  for 
it  blends  gradually  with  the  imperceptible  ether  which  fills  inter- 
planetary space.  While  its  functions  are  less  apparent  than 
those  of  water  and  soil,  it  nevertheless  bears  important  relations 
to  agricultural  life  and  industries. 

Weight  of  the  air.  The  resistance  which  air  offers  to  rapidly 
moving  bodies,  its  own  motion  as  wind  and  the  support  of  clouds 
and  other  bodies  are  evidences  of  its  mass.  The  pressure  by 
which  it  forces  water  into  the  vacuum  of  a  pump  or  balances  a 
column  of  mercury  in  the  barometer  is  a  measure  of  its  weight, 
which  is  approximately  15  pounds  per  square  inch  at  sea  level, 
or  41,300  tons  for  each  acre  of  the  earth's  surface.  Were  the  air 
of  uniform  density  throughout,  its  height  could  be  easily  meas- 
ured. The  barometer  falls,  however,  with  decreasing  rapidity  as 
it  is  raised  from  the  earth,  thus  proving  that  the  air  decreases 
in  density  with  increase  in  height. 

Height  of  the  air.  The  band  of  haze  attending  the  earth's 
shadow  at  lunar  eclipse,  the  twilight  period  upon  the  earth,  the 
time  of  falling  meteors  and  other  phenomena  dependent  upon  the 
atmosphere  give  means  of  estimating  its  approximate  height  as 
at  least  200  miles. 

Air  essential  to  life.  If  an  animal  be  enclosed  with  a  supply 
of  food  in  a  perfectly  tight  chamber  but  with  a  limited  supply  of 
air  it  will  finally  suffocate.  This  occurs  as  a  result  of  exhausting 
the  greater  part  of  a  constituent  of  the  air  known  as  oxygen. 
This  element  is  absolutely  essential  to  the  processes  by  which  food 
is  assimilated  and  waste  matter  is  expelled  from  the  animal  body. 
So  too,  if  a  plant  be  similarly  enclosed,  it  will  finally  cease  to  grow 
and  prematurely  die.  This  is  because  it  exhausts  the  limited  sup- 


24  Agricultural  (Ih 

ply  of  carbon  dioxide,  a  constituent  of  the  air,  which  is  the  basal 
material  for  all  compounds  made  by  the  growing  plant.  The 
burning  of  wood  is  a  chemical  process  in  which  oxygen  of  the  air 
unites  with  the  chemical  constituents  of  the  wood.  If  the  fire  be 
banked  or  otherwise  deprived  of  a  liberal  air  supply,  it  smoulders. 
"When  air  is  liberally  supplied,  as  through  the  stove  drafts  or 
forge  bellows,  combustion — and  the  resultant  heat — are  greatly 
increased,  as  a  consequence  of  the  increased  supply  of  oxygen. 
The  formation  of  humus  in  the  soil,  the  fermentation  of  manures, 
and  many  other  common  phenomena  of  the  farm,  are  in  part  pro- 
cesses of  oxidation  or  burning  on  a  small  scale,  and  are  dependent 
upon  proper  supplies  of  the  oxygen  of  the  air. 

Atmosphere  controls  rainfall.  The  atmosphere  contains  vary- 
ing amounts  of  water.  Warm  air  has  great  capacity  for  holding 
water  and  may  take  up  large  amounts  from  the  sea  and  inland 
lakes.  Movements  of  this  water-laden  air  control  rainfall.  In 
the  case  of  the  warm,  moisture-laden  winds  moving  eatward  from 
the  Pacific  ocean,  the  water  is  released  when  the  air  is  cooled  on 
the  snow  clad  summits  of  the  Rocky  Mountains.  As  a  result,  a 
large  area  east  of  the  mountains,  known  as  the  Great  American 
Desert,  receives  little  or  no  rainfall  and  farmers  are  forced  to 
irrigate  or  practice  dry  farming  on  arable  land  of  this  region. 

Atmosphere  controls  temperature.  Dry  air  transmits  heat 
readily  from  the  sun  to  the  earth  or  from  the  earth  into  space. 
For  this  reason  the  temperature  falls  rapidly  after  sunset  in  dry 
winter  weather.  Dry  air  also  permits  rapid  evaporation  of  water 
from  the  earth's  surface  with  consequent  cooling.  Moist  air,  on 
the  other  hand,  prevents  rapid  evaporation  from  the  earth's  sur- 
face, absorbs  heat  transmitted  from  the  sun  and  radiated  from 
the  earth,  and  thereby  maintains  higher  temperatures. 

While  the  phenomena  of  temperature,  moisture  content,  and 
movement  of  the  air  do  not  directly  involve  chemical  processes, 
they  have  fundamental  significance  in  the  supplying  of  water  and 
the  maintaining  of  temperatures  which  regulate  the  chemical  pro- 
cesses of  plant  growth.  This  significance  has  been  a  prominent 


The  Atmosphere. 


25 


factor  in  the  development  of  the  present  extensive  Weather 
Bureau  service  of  the  United  States  government.  The  records 
of  this  Bureau  are  of  great  service  not  only  in  predicting  storms 
and  frosts,  but  in  mapping  restricted  areas,  such  as  the  sugar  beet 
belt,  which  will  be  favorable  for  certain  crops  dependent  upon 
uniform  temperature  and  proper  amounts  of  sunshine  and  rain- 
fall. 

Air  is  a  mixture.  A  chemical  compound  is  characterized  by 
uniform  composition.  That  is,  the  constituents  of  a  single  com- 
pound occur  in  the  same  proportions  throughout  its  mass.  This 
is  not  true  for  air,  as  the  following  table  shows : 

Percentage  Composition  of  the  Atmosphere  at  Different  Levels. 


Height  in  feet 

3280 

32,800 

65,600 

164,000 

328,000 

Nitrogen              .             

Per  cent 
78.04 
20.99 
0.94 
0.03 

Per  cent 
81.05 
18.35 
0.58 
0.02 

Per  cent 

85.99 
13.79 
0.22 
0.004 

Per  cent 
89.62 
10.31 
0.07 
0.00 

Per  cent 
95.35 
4.65 
0.00 
0.00 

Oxveen  .  . 

Argon                           .            .... 

Carbon  dioxide         

The  air  is  a  mixture  of  water  vapor,  gases,  and  solids  in  which 
the  gases  form  far  the  greatest  part.  Since  it  is  a  mixture,  the 
constituents  are  free  to  separate  and,  as  the  above  table  shows,  the 
heavier  constituents  are  absent  in  the  higher  layers. 

Composition  of  air.  The  average  composition  of  dry  air  is  as 
shown  in  the  table  on  page  26. 

Water  of  the  atmosphere.  The  water  used  by  plants  is  taken 
up  from  the  soil  by  way  of  the  roots.  Its  passage  through  the 
plant  and  the  escape  of  excess  of  water  are  regulated  by  the 
process  of  transpiration  or  evaporation  from  the  surface  of  the 
leaves  into  the  air.  From  the  current  of  water  thus  maintained 
from  the  soil  to  the  plant,  growing  crops  assimilate  all  of  their 
food  except  carbon  dioxide.  When  the  air  is  dry  it  absorbs  water 
readily  and  promotes  transpiration.  Moist  air,  on  the  contrary, 


26 


Agricultural  Chemistry. 


retards  transpiration.     By  these  influences   over  transpiration 
the  air  exercises  control  over  plant  growth. 

As  has  been  stated,  the  presence  of  water  in  the  air  increases 
its  capacity  to  absorb  heat  and  when  the  air  is  cooled  it  loses  its 
power  to  retain  moisture.  Water  then  separates  from  it  and 
collects  upon  colder  objects.  This  is  the  cause  of  the  appearance 
of  drops  of  water  on  the  outer  surface  of  an  ice- water  pitcher  on 
a  sultry  day  in  summer.  Dew  is  formed  in  the  same  manner. 
After  sunset  on  a  warm  summer's  day  the  earth  cools  rapidly 
by  radiation  and  reaches  a  temperature  below  that  of  the  adja- 

The  Average  Composition  of  Dry  Air. 


Per  cent,  bv  weight 
Lbs.  per  100  Ibs. 
of  air. 

Percent,  by  volume 
Gals,  per  100  gals, 
of  air. 

Gases'    Nitrogen          

75.5 

78  0 

Oxygen  .       

23  0 

21  0 

Argon  

1  0 

0  94 

Carbon  dioxide  
Ammonia  
Nitric  acid  
Ozone 

0.04 
Trace 

i 

0.03 
Trace 

Solids:    Dust  

i 

Bacteria  

« 

Salts  

i 

cent  air.  At  a  temperature  bearing  a  definite  relation  to  the 
moisture  content  of  the  air  and  known  as  "the  dew  point," 
moisture  leaves  the  air  and  collects  upon  the  surface  of  vegeta- 
tion and  other  cool  objects.  In  rainless  regions  dew  becomes  an 
important  source  of  water  for  crops  and  frequent  tilling  must 
be  practiced  to  prevent  its  escape  by  evaporation  from  the  sur- 
face of  the  soil. 

Movements  of  the  moisture  laden  air  distribute  rainfall  over 
the  land ;  and  some  of  the  less  prominent  constituents  of  the  air 
are  washed  to  the  soil  by  rain  and  become  factors  in  the  supply 
of  plant  food. 


The  Atmosphere.  27 

Gases  of  the  air.  Dry,  pure  air  is  essentially  a  mixture  of 
gases.  A  gas  differs  from  the  more  familiar  forms  of  matter, 
as  liquids  and  solids,  in  that  its  particles  are  much  farther  re- 
moved from  one  another,  or  as  we  say,  it  has  less  density.  This 
relation  is  illustrated  by  the  different  forms  which  water  may 
assume.  When  the  solid  substance  known  as  ice  is  heated,  its 
particles  spread  farther  apart  until  it  no  longer  has  sufficient  co- 
hesive power  to  retain  its  shape.  It  then  melts  and  becomes  the 
liquid  known  as  water.  Sufficient  further  heating,  by  separating 
the  particles  of  water  still  farther  apart,  transforms  it  to  the 
state  of  an  invisible  gas  known  as  steam,  which  becomes  a  con- 
stituent of  the  gaseous  atmosphere.  When  steam  comes  in  con- 
tact with  cold  solid  objects,  or  even  with  cold  air,  it  contracts 
or  condenses  to  visible  water  vapor.  The  gases  of  the  air  main- 
tain their  rarified  form  under  all  ordinary  conditions.  They  can 
be  converted,  however,  like  the  air  itself,  to  liquids,  and  even 
to  solids,  by  subjecting  them  simultaneously  to  very  low  tem- 
peratures and  high  pressures. 

Nitrogen.  This  is  the  most  considerable  constituent  of  the 
air  and  amounts  to  more  than  three-quarters  of  the  total  weight, 
or  about  30,000  tons  over  every  acre  of  land.  It  is  characterized 
by  extreme  inertness.  When  combined  in  chemical  compounds 
it  is  frequently  held  with  difficulty.  High  power  explosives  de- 
pend for  their  value  upon  the  ready  and  sudden  release  of  a 
large  volume  of  gaseous  nitrogen  from  less  bulky  compounds  as 
nitro-cellulose  and  nitro-glycerine.  Since  nitrogen  is  an  essential 
constituent  of  compounds  of  the  greatest  importance  in  the  living 
cells  of  plants  and  animals,  its  ready  escape  from  such  com- 
pounds has  presented  one  of  the  greatest  problems  of  agriculture. 

Relation  of  nitrogen  to  plant  growth.  The  work  of  several 
able  investigators  has  proved  conclusively  that  higher  plants  can- 
not draw  directly  upon  the  great  stores  of  nitrogen  in  the  air  for 
their  supply  of  this  element. 

In  1855  the  French  chemist  Boussingault  announced  the  re- 
sults of  a  series  of  carefully  performed  experiments  to  determine 


28 


Agricu Itura I 


this  point.  He  grew  plants  for  one  and  one-half  to  five  months 
with  no  nitrogen  supply  beyond  that  in  the  seeds  and  the  free 
nitrogen  of  the  air.  The  seed  was  sown  in  a  soil  composed  of 
ignited  pumice  stone  and  the  ashes  of  manure,  both  having  been 
freed  from  nitrogen  compounds.  The  plants  were  grown  in  a 
glass  jar  sealed  from  the  air  but  in  connection  with  a  supply  of 
carbonic  acid  and  were  provided  also  with  water  free  from  nitro- 
gen. At  the  end  of  the  experiments  the  nitrogen  was  determined 
in  the  plants  and  soil. 

The  following  table  gives  the  results  of  five  of  the  experiments 
and  the  average  of  the  series : 


~r 
Kind  of  Plant. 

Nitrogen  in 
Seeds. 

Nitrogen  in 
Crop  and 
Soil. 

Gain  (-f-)  or 
Loss(-) 
of  Nitrogen  . 

Bean  

gms.* 
0  0349 

gms. 
0  0340 

gms. 
—0  0009 

Oat  

0-0081 

0  0030 

—0  0001 

0.0200 

0-0204 

-1-0  .  0004 

Lupin  

0  0399 

0  0397 

—0  0002 

Cress  

0.0013 

0-0013 

0  0000 

Sum  of  14  Experiments  

0  6135 

0.5868 

—0  0247 

*A  gram  is  about  one-twenty-eighth  of  an  ounce. 

Since  the  gains  or  losses  of  nitrogen  are  within  the  limits  of 
experimental  error,  Boussingault  concluded,  as  a  result  of  his 
work,  that  plants  cannot  use  the  free  nitrogen  of  the  air. 

This  work  was  disputed  by  Ville,  also  of  France,  who  grew 
plants  in  larger  chambers  and  renewed  the  supply  of  air.  He 
criticised  Boussingault 's  work  for  the  limited  amount  of  air 
used.  Boussingault  then  proved  by  further  experiments  that 
plants  raised  under  the  conditions  of  his  earlier  trials  only  at- 
tained full  development  when  supplied  with  assimilable  com- 
pounds of  nitrogen.  An  investigation  of  Ville 's  experiments 
then  showed  that  his  results  were  vitiated  by  the  presence  of 
ammonia  in  his  apparatus. 


The  Atmosphere.  29 

The  problem  concerning  the  assimilation  of  free  nitrogen  was 
finally  settled  by  an  exhaustive  study  made  in  1857  to  1858  by 
Lawes,  Gilbert  and  Pugh  at  the  Rothamsted  Experiment  Station 
in  England.  These  investigators  completed  27  experiments  with 
cereals,  legumes  and  buckwheat.  The  plants  were  grown  under 
glass  jars  inverted  in  mercury  to  isolate  them  from  the  air.  A 
supply  of  air,  freed  from  nitrogen  compounds  and  mixed  with 
carbonic  acid  was  forced  through  the  apparatus  and  all  nitrogen 
compounds  were  carefully  excluded  from  the  soil  and  water  used 
in  these  experiments.  The  results  fully  confirmed  the  conclu- 
sions of  Boussingault. 

In  the  course  of  other  experiments  it  was  observed  that  while 
supplies  of  nitrogen  compounds  in  the  soil  stimulated  the  growth 
of  cereals,  they  were  without  appreciable  effect  upon  legumes. 
It  remained  for  the  German  bacteriologist,  Hellriegel,  to  dem- 
onstrate that  leachings  from  soils  cropped  to  legumes  stimulated 
the  growth  of  these  crops  on  infertile  soils,  but  failed  to  affect 
cereals.  Then  followed  the  discovery  of  a  remarkable  affiliation 
of  bacteria  and  leguminous  plants  by  which  the  plants  obtain 
supplies  of  nitrogen  from  the  atmosphere.  This  discovery  finds 
a  practical  application  in  the  growth  of  leguminous  crops  in 
rotations  for  the  purpose  of  maintaining  the  supply  of  nitrogen 
in  the  soil.  In  field  experiments  the  soil  supply  of  nitrogen  has 
been  maintained  by  growing  clover  in  rotation  with  cereal  crops. 
A  small  amount  of  nitrogen  compounds  also  accumulates  in  the 
soil  by  the  growth  of  bacteria  which  thrive  independently  of 
higher  plants. 

Oxygen.  This  constituent  of  the  air  is  prominent  among  the 
chemical  elements  because  of  its  extreme  activity.  It  combines 
with  the  waste  products  from  plant  or  animal  life  in  the  process 
of  combustion  or  decay  and  makes  possible  their  destruction  and 
removal.  This  process  is  frequently  accompanied  by  perceptible 
heat,  as  in  the  rapid  combustion  of  fuels,  or  the  less  active  com- 
bustion of  manures  and  silage.  It  is  the  source  of  heat  in  the 
animal  body.  The  hardening  of  so-called  "  drying  -oils "  is  also 


30 


Agricultural  Chemistry. 


a  process  of  oxidation.  These  combine  with  the  oxygen  of  the 
air,  in  some  cases  with  sufficient  rapidity  to  produce  a  rise  in 
temperature  causing  spontaneous  combustion.  Destructive  fires 
occasionally  result  from  such  oxidations. 

Oxygen  usually  forms  about  23.2  per  cent  of  the  air  by  weight. 
"Where  animal  life  is  abundant  or  where  much  putrefaction  is  in 
progress,  the  percentage  of  it  in  the  air  will  be  reduced.  On 


Clover  obtaining  its  necessary  nitrogen  from  the  air  through  the  action 
of  certain  bacteria.  No.  5  contains  these  bacteria,  while  No.  6 
does  not  (after  Russell  and  Hastings). 

the  other  hand,  being  exhaled  by  plants,  its  proportion  may  in- 
crease slightly  where  vegetation  is  abundant. 

Argon.  This  gas  forms  most  of  the  remainder  of  the  air.  It 
closely  resembles  nitrogen  in  its  properties.  Argon  is  not  known 
to  be  of  any  importance  to  agriculture. 

Carbon  dioxide.  Although  usually  forming  a  very  small  frac- 
tion of  the  air — 0.04  part,  or  less,  by  weight  in  100  parts  of  air — 
this  constituent  is  of  great  importance  in  agriculture.  The  aver- 
age green  corn  crop  of  12  tons  per  acre  requires  for  its  produc- 
tion 4  tons  of  carbon  dioxide,  which  necessitates  the  respiring  of 
10,000  tons  of  air,  or  about  14  the  amount  available  over  that 


The  Atmosphere.  31 

acre.  This  supply  of  carbon  dioxide  is  assimilated  from  air  taken 
in  through  the  leaf  pores  or  stomata.  When  united  with  water 
brought  from  the  roots,  it  forms  the  basal  compounds  of  the 
plant.  The  removal  of  this  gas  by  plants  is  offset  by  its  return 
from  processes  of  combustion,  fermentation,  and  animal  respira- 
tion so  that  there  is  maintained  a  nearly  constant  proportion  in 
the  air.  When  produced  by  the  decay  of  humus-forming  mate- 
rial, it  dissolves  in  the  soil  water  and  becomes  a  leading  factor 
in  liberating  plant  food  from  the  mineral  compounds  of  the  soil. 

Ozone.  This  gas  bears  the  relation  to  oxygen  of  03 — 02 — 
where  02  is  the  molecular  symbol  for  oxygen.  It  is  one-half  more 
concentrated  than  oxygen  and  as  a  consequence  is  much  more 
active.  Ozone  occurs  in  the  air  as  a  result  of  the  action  of 
electrical  discharges  upon  oxygen.  It  acts  as  an  antiseptic  by  at- 
tacking and  destroying  bacterial  matter.  Because  of  its  great 
activity,  it  is  rapidly  exhausted  and  never  amounts  to  more  than 
a  trace  in  the  atmosphere. 

Nitric  oxide.  Traces  of  this  gas  accumulate  in  the  wake  of 
electrical  storms.  It  is  a  compound  of  one  part  of  nitrogen  with 
one  part  of  oxygen  (14  parts  of  nitrogen  with  16  parts  of  oxy- 
gen by  weight),  the  formation  of  which  is  induced  by  electrical 
discharges.  Nitric  oxide  readily  unites  with  oxygen  and  water 
to  form  nitric  acid  and  washes  to  the  soil  in  the  rain.  Knop 
found  ordinary  rain  water  at  Leipsig,  Germany,  to  contain  56 
pounds  of  nitric  acid  in  10,000,000  pounds  of  water,  while  rain 
which  fell  during  a  thunder  shower  contained  98  pounds  in  10,- 
000,000.  Nitric  acid  brought  to  the  earth  in  this  way  is  not  free 
but  combined  with  ammonia  in  the  air.  Reaching  the  soil  as 
ammonium  nitrate  it  is  directly  available  to  the  plant. 

Ammonia.  This  gas  accumulates  in  traces  in  the  air  as  a  re- 
sult of  the  decay  of  organic  nitrogenous  compounds.  It  is  pro- 
duced in  considerable  amounts  by  the  rapid  fermentation  of 
manures  and  in  such  cases  may  be  detected  by  its  pungent  odor. 
It  dissolves  readily  in  water  and  washes  to  the  soil  in  rains,  gen- 
erally in  combination  with  nitric  acid.  In  this  form  its  nitrogen 


32  Agricultural  Chemistry. 

may  be  used  directly  by  the  plant  or  ultimately  converted  to 
nitrates.  Ammonia  from  this  source  contributes  but  a  small 
part  of  the  nitrogen  required  by  crops. 

The  average  amount  of  nitrogen  brought  to  the  soil  per  acre 
yearly  by  rain  at  the  Rothamsted  Experiment  Station,  over  a 
period  of  1 8  years  was  as  follows : 

Nitrogen  as  nitrates  and  nitrites 1 . 1  Ibs . 

Nitrogen  as  Ammonia 2 . 6  Ibs . 

Nitrogen  in  organic  forms 1 . 0  Ib . 

Total  nitrogen 4 . 7  Ibs. 

Obviously  this  supply  of  nitrogen  falls  far  short  of  the  50  to 
100  pounds  of  nitrogen  per  acre  required  by  different  crops. 

Solids.  The  solids  usually  present  in  common  air  are  sub- 
stances which  have  been  taken  up  by  the  wind  and  remain  sus- 
pended in  finely  divided  condition.  They  include  bacteria,  yeast 
spores  and  other  microscopic  forms  of  plant  life.  These  furnish 
the  nitrogen  already  referred  to  as  brought  to  the  soil  in  '  *  organic 
forms."  The  air  contains  dust  particles  from  finely  divided  soil 
and  this  constituent  is  prominent  in  dry  regions.  Spray  from 
bodies  of  salt  water,  when  taken  into  the  air  by  wind,  evaporates 
and  leaves  small  quantities  of  salts  suspended.  These  consist 
principally  of  sulphates  and  chlorides  of  sodium,  potassium,  cal- 
cium and  magnesium.  Salts  may  be  returned  to  the  soil  by  rain 
in  considerable  amounts  near  the  sea  coast.  Common  salt  is 
brought  to  the  soil  in  this  manner  at  the  rate  of  186  pounds  per 
acre  yearly  at  Georgetown,  British  Guiana ;  at  Rothamsted,  Eng- 
land, which  is  farther  inland,  the  amount  is  about  24  pounds  per 
acre.  Sulphur  is  an  important  element  in  the  growth  of  plants, 
and  is  brought  to  the  soil  by  rain  in  the  form  of  sulphates  taken 
up  from  the  sea.  These  supplies  of  plant  food  may  become  im- 
portant factors  in  the  growth  of  crops.  It  has  been  estimated 
that  the  chlorine  in  rain  water  at  Rothamsted  is  sufficient  for 
crops,  with  the  possible  exception  of  mangels,  and  that  the  sul- 
phur supplied  in  this  way  meets  the  demands  of  most  cultivated 
crops.  This  high  supply  of  sulphur  may,  however,  be  derived 


The  Atmosphere. 


33 


partly  from  extensive  soft  coal  burning  in  a  country  like  Eng- 
land. It  is  extremely  doubtful  if  the  sulphur  supply  from  the 
atmosphere  in  the  open  country  of  the  United  States  is  as  high 
as  that  found  at  Rothamsted.  It  is  very  probably  much  lower 
and  not  nearly  sufficient  for  continuous  crop  requirements. 

Accidental  constituents.  In  some  localities  the  air  contains 
uncommon  constituents  as  a  result  of  local  conditions.  This  is 
true  in  active  volcanic  regions  and  in  the  vicinity  of  some  indus- 


The  effect  of  smelter  fumes  and  waste  on  vegetation  near  Anaconda, 

Montana. 

trial  plants.  The  most  important  of  these  constituents  are  gases. 
Methane  or  marsh  gas,  which  is  a  product  of  fermentation  where 
air  is  excluded  and  which  accumulates  over  swamps  and  in  mines, 
and  carbon  monoxide,  a  product  from  the  incomplete  combustion 
of  coal,  are  examples  of  this  class.  Hydrochloric  acid  gas.  which 
escaped  into  the  air  in  quantity  from  the  old  process  of  manu- 
facturing soda,  is  an  example  of  an  objectionable,  accidental  con- 
stituent of  the  air  resulting  from  an  industrial  process.  The 
deadly  effect  of  this  gas  upon  vegetation  led  to  the  passage  of 


34  Agricultural  Chemistry. 

laws  restricting  its  escape.  It  is  now  condensed  in  the  factory 
as  a  by-product  of  the  industry. 

Sulphur  dioxide  is  an  accidental  gaseous  constituent  of  the 
air,  the  effects  of  which  are  of  economic  importance.  It  is  ex- 
pelled from  the  stacks  of  smelters  roasting  ores  which  contain 
sulphur.  It  is  also  produced  in  small  amounts  wherever  the 
combustion  of  coal  takes  place.  It  may  be  partially  converted  to 
sulphur  trioxide  and  brought  to  the  soil  by  rain  as  a  supply  of 
sulphur  for  plants.  The  amount  in  the  rain  at  Rothamsted  was 
found  to  be  about  17  pounds  of  sulphur  trioxide  yearly  per  acre. 

Experiments  have  demonstrated  that  sulphur  dioxide  injures 
plants  through  their  leaves.  Fumigation  with  one  part  of  the 
gas  to  100,000  parts  of  air  has  been  fatal  to  scrub  pines.  In- 
vestigations have  shown  it  to  be  the  cause  of  serious  injury  to 
the  vegetation  in  the  vicinity  of  copper  smelters  in  California, 
Montana  and  elsewhere.  The  foliage  of  injured  trees  in  these 
vicinities  was  found  to  contain  more  sulphur  than  that  of  normal 
trees.  Peach  trees  in  an  exposed  position  nine  miles  from  a 
smelter  at  Redding,  California,  and  red  firs  at  a  distance  of  fif- 
teen miles  from  the  Washoe  smelter,  Anaconda,  Montana,  were 
badly  injured.  Analysis  of  the  smoke  from  the  latter  smelter 
showed  an  output  of  5,000,000  pounds  of  sulphur  trioxide  per 
day.  Haywood,  of  the  Bureau  of  Chemistry,  concludes  that  these 
fumes  can  be  condensed  and  the  products  probably  readily  mar- 
keted. Legislation  in  the  interests  of  forestry  should  restrict 
the  escape  of  this  gas  as  it  has  in  the  case  of  hydrochloric  acid. 


CHAPTER  III 
THE  SOIL. 

Soil  is  the  layer  of  disintegrated  rock,  mixed  with  the  remains 
of  plants,  which  covers  a  large  portion  of  the  land.  It  also  con- 
tains living  organisms  of  various  kinds  and  variable  quantities 
of  water  and  air.  The  depth  of  soils  varies  greatly,  being  usually 
from  six  to  twelve  inches,  and  sometimes  as  great  as  several  feet. 
Beneath  it  is  the  subsoil  which  differs  from  the  upper  layer  in 
containing  less  organic  matter.  The  line  of  demarcation  can 
often  be  distinctly  seen  in  deep  trenches  by  the  difference  in  color, 
the  subsoil  being  generally  of  lighter  color,  and  gradually  grad- 
ing into  the  dark  color  of  the  upper  soil. 

Soils  consist  largely  of  disintegrated  rock  fragments  and  de- 
pend for  their  chemical  nature  mainly  upon  the  character  of  the 
rocks  beneath.  The  rocks  have  been  classified  by  geologists  ac- 
cording to  their  origin  into  three  classes : 

(1)  Igneous  rocks  are  those  which  resulted  from  the  cooling 
of  intensely  heated  matter.     The  granites  represent  this  type. 

(2)  Sedimentary  rocks  are  those  resulting  from  the  settling 
out  of  particles  suspended  in  water.     Limestones  are  examples 
of  this  type. 

(3)  Metamorpkic  rocks  are  those  which  have  been  changed  in 
character  since  their  deposition.     The  conversion  of  limestone 
into  marble  by  pressure  and  heat  is  an  illustration  of  this  type. 

These  rocks  must  have  contained  all  of  the  mineral  or  ash  ele- 
ments of  plant  food  as  no  other  source  for  them  is  conceivable. 

Rocks  are  rarely  homogeneous,  that  is,  alike  in  all  parts — but 
are  generally  made  up  of  several  components  mingled  together, 
often  lying  side  by  side  as  separate  crystals.  These  components, 
which  have  a  more  or  less  definite  composition,  are  called  min- 
erals. Distinctly  separate  minerals  are  more  frequently  to  bo 
seen  in  the  igneous  rocks.  A  piece  of  granite  will  readily  show 
that  it  is  made  up  of  several  distinct  minerals. 


36  Agricultural  Chemistry. 

Minerals.  The  following  minerals  are  abundant  and  of  the 
greatest  importance  to  agriculture: 

Quartz  is  chemically  a  compound  of  silicon  and  oxygen.  It 
is  estimated  that  it  forms  35  per  cent  of  the  solid  crust  of  the 
earth.  It  is  one  of  the  hardest  and  most  durable  of  substances 
and  is  practically  insoluble  in  water  and  but  little  affected  by 
the  weather.  Sea  sand  and  the  sands  along  the  shores  of  our 
fresh  water  lakes  are  often  almost  wholly  made  up  of  fine  grains 
of  quartz,  worn  smooth  by  continuous  agitation  to  which  they 
have  been  subjected.  Fragments  of  quartz,  consisting  of  crystals 
rounded  and  worn  by  mechanical  rubbing  against  each  other, 
form  the  largest  constituent  of  many  soils.  Such  sand  is  lack- 
ing in  plant  food. 

Feldspars  are  probably  the  most  abundant  of  all  minerals  and 
constitute,  it  is  estimated,  48  per  cent  of  the  earth 's  crust.  Chem- 
ically, the  feldspars  contain  silicon,  oxygen  and  aluminum  in 
combination  with  either  sodium,  potassium,  or  calcium,  and  are 
called  by  the  chemist,  silicates. 

The  chief  varieties  of  feldspars  are 

Orthoclase  potassium    aluminum     silicon     oxygen 

Albite sodium         aluminum    silicon    oxygen 

Labrador!  te sodium         aluminum     silicon    oxygen 

calcium 

Orthoclase  or  potash  feldspar  is  the  most  important.  It  is  a  hard 
mineral,  often  colored  pink  or  green,  though  sometimes  white. 
Although  hard,  it  is  easily  attacked  by  water  and  carbon  dioxide, 
the  potassium  being  largely  removed  in  solution  while  the  final 
residue  is  kaolin  or  China  clay.  Orthoclase  furnishes  a  consider- 
able quantity  of  the  potash  found  in  our  soils. 

Mica  is  another  abundant  mineral  and  characterized  by  its 
tciid'-ncy  to  split  into  thin  elastic  plates.  It  is  essentially  a  com- 
pound of  aluminum,  potassium,  silicon  and  oxygen,  though  it 
usually  contains  iron  and  often  calcium  or  magnesium.  Mica 
also  suffers  decomposition  under  the  influence  of  the  weather, 
but  not  so  readily  as  the  feldspars.  It  furnishes  plant  food  in 


The  Soil.  37 

the  iron,  potassium  and  calcium  it  contains.  Its  amount  in  the 
earth's  crust  has  been  estimated  at  8  per  cent. 

Silicates  of  magnesia  are  also  very  abundant.  Talc  and 
steatite  are  representatives  of  this  class  and  are  compounds  of 
magnesium,  silicon  and  oxygen,  designated  by  the  chemist  "sil- 
icates of  magnesia. ' '  They  also  contain  water.  When  the  mag- 
nesium is  partly  replaced  by  other  elements,  as  calcium,  iron  or 
manganese,  we  have  the  distinct  minerals  known  as  hornblende 
and  augite.  All  the  minerals  of  this  class  are  easily  acted  upon 
by  water  and  air  and  often  yield  brightly  colored  clays  due  to 
the  presence  of  iron. 

Calcium  carbonate  occurs  in  a  great  many  crystalline  forms, 
the  principal  variety  being  called  calcite,  and  in  the  massive  form 
is  known  as  chalk,  limestone  and  marble.  These  are  all  essen- 
tially made  of  calcium,  carbon  and  oxygen,  but  in  certain  local- 
ities the  calcium  is  more  or  less*  replaced  by  magnesium  which 
then  gives  us  the  mineral  known  as  dolomite.  This  is  true  of 
many  of  the  "limestones"  found  in  Wisconsin.  Most  calcium 
carbonates  contain  notable  quantities  of  phosphoric  acid.  Cal- 
cium and  magnesium  carbonates,  though  only  slightly  soluble  in 
pure  water,  are  readily  soluble  in  water  containing,  as  in  the  case 
of  nearly  all  forms  of  natural  water,  carbon  dioxide.  Rocks  con- 
taining these  substances  therefore  are  quickly  eroded  by  exposure 
to  the  atmosphere.  Calcium  carbonate  is  of  great  importance  in 
soils,  both  on  account  of  its  providing  plant  food  and  because 
of  its  relationship  to  many  of  the  processes  which  go  on  in  soils. 

Clay  in  its  pure  form  is  a  hydrated  silicate  of  aluminum  and 
is  therefore  devoid  of  plant  food.  By  the  term  hydrated  we 
mean  that  the  compound  of  silicon,  aluminum  and  oxygen  (sili- 
cate of  aluminum)  is  joined  to  a  certain  amount  of  water.  Or- 
dinary clay,  however,  contains  iron  and  potassium,  the  latter  re- 
maining from  the  feldspar,  from  which  most  clays  have  been 
formed.  It  therefore  supplies  potassium  to  plants.  Its  physical 
properties  are  very-  important  and  greatly  influence  soils  in 
which  it  is  abundant. 


38  Agricultural  Chemistry. 

Apatite  or  crystalized  phosphate  of  lime,  is  present  in  small 
quantities  in  many  of  the  older  rocks,  and  is  probably  the  original 
source  of  the  phosphoric  acid  of  soils.  Apatite  also  occurs  mas- 
sive in  some  of  the  older  rock  formations  and  is  mined  as  a  raw 
material  for  the  manufacture  of  phosphate  manure  in  Norway, 
Canada  and  particularly  in  some  of  our  southern  states,  as  Flor- 
ida, the  Carolinas,  Georgia  and  Tennessee. 

A  brief  description  of  some  of  the  more  important  rocks  will 
now  be  given.  The  igneous  rocks  are  the  oldest  and  it  was  from 
the  debris  of  igneous  rocks  that  sand  stones,  shales  and,  indirect- 
ly, limestones  were  formed. 

Sand  stones  and  grits,  consist  of  the  larger  fragments  of  the 
waste  resulting  from  the  breaking  up  of  igneous  rocks,  as  for 
example  granite,  which  in  consequence  of  their  size  and  weight 
have  been  deposited  at  or  near  the  mouths  of  rivers.  Their  main 
ingredient  is  silica,  the  grains  of -sand  consisting  largely  of  quartz 
crystals,  but  in  many  cases  fragments  of  feldspars,  mica  and 
other  minerals  are  present.  These  grains  are  cemented  together 
either  by  calcium  carbonate,  as  in  calcareous  sand-stones,  by  clay, 
as  in  argillaceous  sand-stones,  by  iron  oxide,  as  in  ferruginous 
sand-stones,  or  by  silica,  as  in  siliceous  sand-stones.  Soils  pro- 
duced by  the  decay  of  sand-stones  are  light  and  friable  and  poor 
in  plant  food  unless  there  is  present  potassium-containing  min- 
erals as  feldspar  and  mica. 

Shales  consist  principally  of  the  plastic  hydrated  aluminum 
silicate,  kaolin,  but  may  contain  any  other  extremely  finely  di- 
vided matter  obtained  by  the  erosion  of  the  original  rock.  Par 
tides  of  undecomposed  or  partially  decomposed  feldspars  are 
often  present  and  these  are  of  importance  because  of  the  potasli 
they  contain.  Soils  formed  from  shales  are  "heavy"  and  cl.-iycy. 
generally  sufficiently  rich  in  potassium,  but  poor  in  phosphorus 
and  calcium  carbonate  (lime). 

Limestones,  in  which  term  chalk  and  magnesian  limestone  m;iy 
also  be  included,  have  been  formed  largely  by  the  abstraction 
from  water  by  living  organisms,  as  coral  polyps,  shell  fish,  etc., 


The  Soil  39 

of  calcium  and  magnesium  carbonates.  Oyster  shells  are  prin- 
cipally a  calcium  carbonate.  Limestones  often  contain  small 
quantities  of  clay,  iron  oxide,  silica  and  nearly  always  calcium 
phosphate  in  comparatively  large  quantities.  The  soil  left  on 
limestone  or  chalk  consists  mainly  of  these  foreign  substances, 
most  of  the  calcium  carbonate  it-self  having  been  dissolved  out 
by  the  combined  action  of  water  and  carbon  dioxide.  It  some- 
times happens  therefore  that  the  soil  originating  on  limestone 
would  be  benefited  by  an  application  of  limestone. 

Limestone  only  exerts  its  characteristic  and  importanf  func- 
tions in  a  soil  when  in  a  very  finely  divided  state.  In  the  form 
of  gravel  or  sand  it  is  little  better  than  ordinary  siliceous  sand. 
In  the  finely  divided  state  it  has  two  very  valuable  functions; 
first,  as  a  source  of  plant  food  by  virtue  of  the  calcium  which  it 
contains,  and  second,  which  is  more  important,  as  a  basic  material 
necessary  for  the  correction  of  an  acid  reaction  in  the  soil  and 
for  the  processes  of  nitrification. 

Sedentary  and  transported  soils.  These  terms  are  convenient 
in  distinguishing  between  soils  which  have  been  made  up  of  the 
debris  resulting  from  the  weathering  of  the  particular  rock  on 
which  they  rest  (sedentary  soils)  and  those  which  owe  their 
origin,  not  to  the  rock  below  them,  but  to  materials  brought  from 
a  distance  and  deposited  there  (transported  soils).  The  rich 
alluvial  soil  in  the  lower  reaches  of  river  valleys  consists  largely 
of  material  which  has  been  brought  down  by^  the  river  from  the 
higher  parts  of  the  valley  and  since  the  materials  in  many  cases 
have  been  brought  from  various  rock  formations,  the  resulting 
soil  generally  possesses  a  greater  fertility  than  would  be  shown 
by  soil  formed  exclusively  by  the  weathering  of  any  one  kind  of 
rock. 

Glaciers  are  also  the  means  of  transporting  large  quantities  oi* 
materials  out  of  which  soils  may  be  formed.  Large  tracts  of 
country  are  covered  with  a  thick  deposit  of  clay  and  rock  frag- 
ments, which  have  been  brought  from  a  great  distance  by  glaciers. 
Such  deposits  are  known  as  glacial  drift,  and  often  quite  obscure 


-10 


Agricultural  Chemistry. 


the  actual  rock  beneath.  In  this  case  the  transportation  of  the 
soil  took  place  many  ages  ago.  A  large  part  of  northern  United 
States  is  covered  by  drift,  which  was  pushed  down  from  the  north 
by  the  glaciers  that  once  covered  that  section  and  was  left  behind 
as  the  ice  melted  away.  Such  soils  are  distinguished  from  all 


The  weathering  of  rock  into  sub-soil  and  soil  (after  Hall). 

others  by  the  presence  of  rounded  boulders  of  various  sizes. 
They  are  usually  fertile,  although  very  variable  in  composition. 

Wind  also  sometimes  acts  as  a  means  of  transporting  sand, 
volcanic  ash,  etc.,  from  a  distance  and  deposits  them  in  a  new 
position,  there  to  form  a  soil. 

Formation  of  soil.  In  the  formation  of  a  soil  the  first  step 
is  the  mechanical  breaking  down  of  the  rock  into  small  fragments. 


The  Soil.  4L 

The  chief  agencies  by  which  this  is  accomplished  are,  first  by 
Water,  which  acts  in  several  ways. 

Mechanically,  by  liquid  water — The  flow  of  water  over  the 
surface  of  a  rock  abrades  it  slightly.  The  action  is  greatly  in- 
creased by  the  nibbing  action  of  pebbles  and  gravel,  urged  on 
by  the  current  over  the  rock.  In  this  way  streams  in  the  rapid 
portions  of  a  course  carry  away  large  quantities  of  sand,  gravel, 
etc.,  and  deposit  them  in  the  lower  and  quieter  portions  of  their 
course  as  alluvial  deposits.  By  glaciers — Glaciers  are  slowly 
moving  masses  of  ice.  In  their  descent,  aided  by  fragments  of 
rock  imbedded  in  them,  they  grind  away  the  rock  over  which 
they  pass  and  the  stream  which  flows  from  the  base  of  a  glacier 
is  always  heavily  charged  with  the  finest  mud,  while  the  lowest 
point  reached  by  a  glacier  is  marked  by  huge  piles  of  rock  frag- 
ments of  all  sizes,  carried  down  on  the  surface  of  the  moving  ice. 
By  alternate  frost  and  thaw — Ice  occupies  a  greater  volume  than 
the  water  from  which  it  is  formed.  The  increase  in  volume  in 
the  act  of  freezing  amounts  to  about  10  per  cent  and  unless  this 
increase  is  allowed  to  occur  water  cannot  freeze,  however  much 
it  be  cooled.  This  is  a  powerful  agency  in  the  pulverization  of 
rocks.  All  rocks  are  more  or  less  porous  and  absorb  Vater. 
During  the  warm  part  of  a  wet  winter's  day  the  crevices  of  a 
rock  become  filled  with  water.  If  the  temperature  falls  the 
water  begins  to  freeze,  at  first  on  the  surface  so  that  every  crevice 
becomes  plugged  with  ice.  As  the  liquid  within  continues  to  lose 
heat  it  tends  to  solidify.  This  it  can  only  do  if  it  be  allowed  to 
expand  and  in  order  to  do  this  it  must  widen  or  lengthen  the 
crevice.  When  the  next  thaw  comes,  the  enlarged  crevice  again 
fills  with  water.  The  next  freeze  repeats  the  action  and  so  the 
process  goes  on  until  the  hardest  rock  is  broken  into  fragments. 

Chemically.  Many  minerals  when  exposed  to  the  action  of 
water  are  acted  upon  in  such  a  way  as  to  load  to  their  disintegra- 
tion. A  portion  is  often  carried  away  in  solution  while  the  re- 
mainder crumbles  and  is  then  easily  moved  by  rain  or  running 
water.  In  many  rocks  the  cementing  material,  which  holds  the 


42  Agricultural  Chemistry. 

grains  together,  is  dissolved  away  and  the  residual  fragments 
then  readily  crumble. 

A  soil  produced  by  mere  mechanical  pulverization  of  the  rocks 
would  not  furnish  proper  food  for  the  higher  plants.  This  can 
readily  be  imagined  if  one  thinks  how  unsuitable  crushed  granite 
would  be  for  plant  production.  The  essential  elements  locked 
up  in  these  insoluble  soil-forming  materials  must  be  changed  into 
materials  that  the  plant  can  assimilate  and  water  is  an  important 
factor  in  bringing  about  such  chemical  changes.  The  minerals 
forming  our  igneous  rocks  are,  however,  very  slightly  soluble  in 
pure  water;  but  the  water  that  enters  the  ground  has  dissolved 
in  it  small  amounts  of  carbon  dioxide,  derived  from  the  air,  and 
water  containing  this  gas  will  dissolve  these  minerals  in  appre- 
ciable quantities. 

Another  important  agent  in  soil  formation  is  the  air,  which 
acts  in  several  ways. 

Mechanically.  Wind  actually  detaches  large  projecting  pieces 
of  rock  in  mountainous  districts  and  sends  them  crashing  down 
onto  the  rocks  below.  In  addition,  by  hurling  sand  and  small 
peebles  against  the  surface  of  rocks  it  brings  about  the  erosion  of 
the  latter.  In  most  cases  the  effects  of  this  form  of  erosion  are 
masked  and  hidden  by  those  of  other  denuding  agencies. 

Chemically.  In  many  rocks  are  minerals  capable  of  taking  up 
oxygen.  On  exposure  to  air,  oxidation  occurs  and  the  mineral 
swells  up  and  often  crumbles  to  powder,  thus  loosening  the  other 
minerals  in  the  rocks.  This  oxidation  is  in  many  cases  accom- 
panied by  a  change  in  color,  from  green  or  gray  to  yellow  or 
red.  The  carbon  dioxide  of  the  air  also  acts  corrosively  on  car- 
bonates in  the  presence  of  water. 

Animals  are  also  important  agencies  in  soil  formation.  Bur- 
rowing animals,  as  for  example,  rabbits,  moles,  etc.,  admit  air 
into  soil  or  sand  and  thus  favor  the  changes  which  air  produces. 
The  part  played  by  the  humbler  creatures,  earth  worms,  is  prob- 
ably much  more  important.  They  bring  portions  of  the  subsoil 
to  the  sin  f;icc.  they  draw  dead  leaves  and  other  vegetable  refuse 


The  Soil  43 

into  their  burrows,  and  they  pass  large  quantities  of  the  soil 
through  their  bodies  and  deposit  it  on  the  surface  at  a  rate  which 
has  been  estimated  on  the  average  to  be  about  ten  tons  per  acre 
per  year. 

Ants  in  some  hot  countries,  as  for  example  Africa,  perform 
much  the  same  work  as  earth  worms,  though  perhaps  on  even  a 
larger  scale.  Ingle  says  that  in  many  parts  of  South  Africa,  the 
veld  is  thickly  studded  with  the  hills  of  the  white  ant,  usually 
about  two  feet  high  and  about  two  to  three  feet  in  diameter, 
though  much  larger  ones  are  often  found.  The  ant  hills  are  full 
of  cavities  and  chambers  inhabited  by  the  insects  and  much 
vegetable  matter  is  stored  in  them.  The  material  of  the  ant  hills 
consists  of  the  smaller  parts  of  the  surrounding  soil,  the  par- 
ticles being  cemented  together  and  the  whole  made  practically 
water  tight.  When  the  veld  is  plowed  and  sown,  it  is  always 
noticed  that  where  ant  hills  had  formerly  been  the  crop  is  heavier 
than  elsewhere. 

Plants  act  as  soil  formers  in  several  ways :  Mechanically — the 
roots  penetrate  the  rocks  or  soils,  rendering  them  porous  and  thus 
admitting  air  and  water.  They  also  exert  a  tremendous  lateral 
force,  breaking  apart  rocks  and  stones  when  once  they  have  ob- 
tained a  foothold  in  a  crevice.  The  roots  penetrate  the  soil  some- 
times to  great  depths,  and  as  they  decay,  afer  the  death  of  the 
plant,  they  leave  in  the  soil  little  channels,  which  serve  to  carry 
down  water  laden  with  carbon  dioxide,  as  well  as  the  oxygen 
of  the  air,  which  as  previously  pointed  out  are  important  factors 
in  soil  making  and  the  production  of  available  plant  food. 
Chemically — plants  act  during  life  through  the  corrosive  action 
of  the  carbon  dioxide  excreted  by  the  roots  and  root  hairs  and 
after  death  by  producing  carbon  dioxide  and  various  vegetable 
acids,  which  have  solvent  properties  upon  certain  constituents 
of  soils. 

The  formation  of  a  mass  of  pulverized  rock,  however,  is  not 
all  that  is  necessary  for  producing  a  fertile  soil.  A  fertile  soil 
must  contain  nitrogen.  It  has  been  shown  that  to  grow  crops  the 


44 


Agricultural  Chemistry. 


soil  must  contain  available  nitrogen,  and  this  must  have  been  de- 
rived originally  from  the  air.  Small  quantities  of  combined 
nitrogen,  as  stated  in  a  previous  chapter,  are  carried  into  the 
ground  by  the  rain  water  and  though  small  in  amount,  are  prob- 
ably sufficient  to  enable  plant  growth  to  begin.  Bacteriologists 
believe  that  certain  species  of  bacteria,  which  can  live  on  mineral 
food  alone  and  derive  all  their  nitrogen  supply  from  the  air  were 
the  first  agencies  and  are  still  important  factors  in  accumulating 
the  nitrogen  supply  of  the  soil.  Certain  simple  forms  of  plant 


Diagram  illustrating  the  formation  of  a  soil  on  a  limestone  hill  (after 

Vivian). 

life,  as  lichens  and  mosses,  it  is  believed,  can  also  derive  their  nit- 
rogen from  the  atmosphere.  When,  after  death,  a  plant  becomes  a 
part  of  the  soil,  all  the  plant  food  it  contained  is  returned.  Food, 
once  used  by  plants,  is  readily  made  available  to  succeeding  crops 
through  processes  of  decay  and  nitrification.  The  soil  is  thus 
made  richer  and  more  fertile.  In  this  way  growth  gradually 
becomes  more  abundant.  The  plants  upon  decay  give  rise  to 
"humus,"  the  chief  nitrogen  containing  body  of  the  soil  and 
from  which  the  higher  plants,  through  ammonification  and  nit- 
rification, derive  their  necessary  supply  of  nitrogen. 

Legumes  enrich  soil  with  nitrogen.     This  particular  class  of 
plants  to  which  the  clovers,  alfalfas,  vetches,  lupines,  peas,  and 


/(cati 


The  Soil.  45 

beans  belong,  is  able,  through  the  agency  of  nodule  forming  bac- 
teria growing  on  the  roots,  to  derive  nitrogen  from  the  inex- 
haustible stores  of  the  atmosphere.  This  peculiar  property  of 
leguminous  plants  is  quite  distinct  from  the  requirements  of  all 
other  farm  crops,  which  acquire  their  nitrogen  from  the  nitrogen 
compounds  already  in  the  soil.  This  fact  is  of  the  greatest  im- 
portance to  agriculture,  for  it  is  " Nature's  principal  method'' 
of  increasing  the  nitrogenous  food  in  the  soil.  The  nitrogenous 
compounds  stored  in  such  plants  eventually  become  a  part  of  the 
soil  through  their  decay,  thus  furnishing  food  for  other  plants 

increasing  the  fertility  of  the  soil. 

The  constituents  of  soil.     A  popular  and  convenient  classifi- 
ation  of  soil  constituents  is  the  following : 

(1)  Sand — mainly  silica,  but  containing  small  fragments  of 
feldspar,  mica,  and  other  minerals. 

(2)  Clay — mainly  kaolin,  but  containing  small  fragments  of 
silica,  feldspar,  etc. 

(3)  Limestone — finely  divided  calcium  carbonate. 

(4)  Humus — the  somewhat  indefinite  nitrogenous  and  carbon- 
aceous material,  brown  or  black  in  color  and  resulting  from  the 
decay  of  plants.     A  brief  description  of  these  materials  will  now 
be  given. 

Sand  is  of  low  specific  heat  and  has  the  lowest  water  retaining 
power  of  all  soil  constituents.  It  is  practically  valueless  as  a 
plant  food,  except  for  the  small  amounts  of  potassium,  calcium 
and  iron  contained  in  the  mineral  fragments  mixed  with  the  true 
sand.  Its  physical  properties  often  have  valuable  effects  upon 
the  character  of  a  soil,  particularly  with  regard  to  friability,  and 
its  relation  towards  water  and  heat. 

Clay  in  its  pure  form  is  free  from  plant  food,  but  is  usually 
well  supplied  with  potash,  because  of  the  feldspar  present.  Com- 
mon clay  contains  quartz  and  calcium  carbonate  (as  in  marls) 
in  addition  to  feldspar.  The  true  clay  (kaolin)  acts  as  a  cement 
to  the  other  mineral  grains. 

It  is  thought  that  even  in  the  purest  clay  there  is  a  small  quan- 


46  Agricultural  Chemistry. 

tity  of  aluminum  silicate  containing  more  water  than  the  rest, 
to  which  the  plasticity  and  tenacity  of  clay  is  due.  If  this  con- 
stituent is  fully  swollen  with  water  the  clay  is  impervious  and 
sticky,  while  if  it  is  shrunken  or  coagulated  the  clay  becomes 
more  friable  and  less  plastic.  Calcium  compounds  are  partic- 
ularly effective  in  inducing  such  coagulation  and  it  is  to  this 
cause  that  the  improvement  in  texture  of  heavy  clays  by  lime 
applications  is  due. 

Lime  stone.  Calcium  carbonate  is  present  in  the  soil  in  a  fine- 
ly divided  state  distributed  ^among  the  other  constituents,  but  in 
addition  there  may  be  larger  fragments  which  are  classed  with 
the  "sand."  The  finely  divided  material  is  the  one  of  import- 
ance. It  furnishes  plant  food,  for  the  plant  must  have  calcium, 
but  it  also  plays  other  important  functions.  It  modifies  the 
plasticity  of  clay  in  the  manner  described  above  and  in  addition 
neutralizes  any  acids  accumulating  in  the  soil.  Acids  are  pro- 
duced by  the  decay  and  fermentation  of  vegetable  matter,  and 
if  allowed  to  accumulate,  will  render  the  soil  unfit  for  max- 
imum crop  production.  Such  soils  are  spoken  of  as  "sour"  and 
can  best  be  restored  to  fertility  by  the  application  of  quick  lime 
or  ground  limestone.  Limestone  performs  another  important 
function  by  acting  as  a  basic  material  necessary  for  the  process 
known  as  nitrification,  to  be  explained  later. 

Limestone  also  serves  an  important  function  in  those  soils 
which  have  received  applications  of  the  commercial  fertilizer, 
ammonium  sulphate.  It  prevents  the  accumulation  of  sulphuric 
acid,  which  otherwise  would  make  the  soil  sour,  by  its  power  to 
neutralize  this  acid.  The  neutral  salt  formed — calcium  sulphate 
—partly  runs  off  in  the  drainage  water. 

Humus  is  the  brown  or  black  organic  matter  of  surface  soil. 
It  is  the  product  formed  by  partial  decay  of  organic  matter  and 
is  the  material  that  gives  the  rich  black  appearance  to  some  soils. 
It  is  formed  from  the  residue  of  plants  previously  grown  on  the 
soil  or  from  added  organic  matter  in  farm  manures  or  commercial 
fertilizers.  It  is  a  mixture  of  many  ill-defined  bodies.  Besides 


The  Soil.  47 

the  nitrogen  contained  in  it,  there  is  always  found  in  its  ash, 
such  plant  food  elements  as  phosphorus,  potassium,  iron  and 
sodium,  together  with  silicon  and  aluminum.  These  ash  consti- 
tuents are  thought  to  be  of  considerable  importance  because  they 
are  apparently  easily  available  to  plants. 

The  humus  of  soils  is  of  the  greatest  agricultural  importance. 
It  not  only  modifies  its  physical  properties,  but  is  the  principal 
storehouse  for  nitrogen.  A  soil  rich  in  humus  is  rich  in  nitro- 
gen ;  a  soil  poor  in  humus  is  poor  in  nitrogen.  The  plant  does 
not  use  it  directly,  but  its  nitrogen  must  first  be  converted  by 
bacteria  into  water  soluble  forms,  such  as  nitrates,  before  it  is 
available.  By  the  decay  of  humus  the  proportion  of  carbon  diox- 
ide in  the  soil  water  is  increased  and  thus  the  solvent  powers  of 
the  latter  for  plant  food  in  the,  mineral  portion  of  the  soil  are 
enhanced. 

Virgin  soils  are  comparatively  rich  in  humus,  but  continuous 
cropping  with  no  return  to  the  soil  of  humus  forming  materials 
may  result  in  its  being  decreased  from  one-third  to  one-half  in 
a  period  of  not  more  than  fifteen  years.  The  amount  of  humus 
in  soils  is  variable,  dependent  upon  such  factors  as  climate  and 
the  previous  soil  treatment.  In  humid  regions  ordinary  arable 
soils  vary  in  humus  content  from  2  to  5  per  cent.  Swampy, 
peaty,  and  muck  soils  contain  larger  amounts.  In  a  bog  soil  the 
per  cent  of  humus  may  be  as  high  as  30  per  cent.  In  arid  re- 
gions the  amount  of  humus  in  the  soil  is  normally  less  than  found 
in  our  humid  regions,  the  amount  rarely  exceeding  1  per  cent. 

These  materials  described  above  have  great  influence  upon 
both  the  physical  and  chemical  properties  of  soils.  The  import- 
ant physical  properties  of  the  constituents  themselves  are  shown 
in  the  table  on  page  48. 

The  explanation  of  the  terms  fused  in  the  table  are  as  fol- 
lows: Specific  gravity  is  the  weight  of  any  volume  of  the 
solid  material  compared  with  that  of  an  equal  volume  of  water. 
Specific  heat  (equal  weight)  is  the  ratio  of  the  amount  of  heat 
necessary  to  raise  the  temperature  of  a  certain  quantity  of  a 


48 


A gricultural  Che mistry. 


substance  compared  with  that  required  to  raise  an  equal  weight 
of  water  through  the  same  range  of  temperature.  Specific  heat 
(equal  volume)  is  the  relative  amounts  of  heat  required  to  raise 
equal  volumes  of  the  material  and  of  water  through  a  given  range 
of  temperature. 

Physical  Properties  of  Soil  Constituents. 


Specific 
Gravity 

Specific  Heat 
Equal 
Weight 

Specific  Heat 
Equal 
Volume 

Water  held 
by  100  parts 
by  \veight 
of  substance 

Water 

1.00 

1  000 

1  000 

Sand 

2  62 

.189 

499 

25 

Clay 

2.50 

233 

568 

70 

Limestone  

2.60 

.  206 

.561 

85 

Humus 

1.30 

.477 

587 

181 

From  the  above  table  we  see  that  the  same  quantity  of  heat 
will  raise  1  pound  of  water  and  5  pounds  of  limestone  or  sand 
to  about  the  same  temperature,  or  if  we  consider  only  the  solid 
constituents  of  soil,  the  same  amount  of  heat  will  raise  3  pounds 
of  humus  and  8  pounds  of  sand  to  the  same  temperature. 
^^Relation  to  heat.  The  sources  of  heat  to  a  soil  are  the  sun  and 
chemical  changes  within  the  soil.  The  chemical  oxidation  of 
organic  matter  in  the  soil  will  slightly  raise  the  temperature,  but 
by  radiation  are  largely  influenced  by  weather  conditions.  Ex- 
tremes of  heat  and  cold  occur  with  a  clear  sky  and  dry  air.  In 
a  cloudy,  moist  climate,  the  variations  in  temperature  are  com- 
paratively small.  At  mid-day  the  power  of  the  sun's  rays  is  at 
(iepth  of  1  foot,  the  average  temperature  of  the  soil,  after  a  lapse 
of  20  days  was  2.3°  higher  than  that  of  unmanured  soil.  Dur- 
ing the  next  5  days  the  excess  of  temperature  was  only  0.8°. 
Chemical  action  is  at  its  height  during  the  summer  months. 

The  amount  of  heat  received  from  the  sun  and  the  amount  lost 
the  effect  is  generally  sligh^  (  In  an  experiment  at  Tokio,  J;ip«-m. 


The  Soil.  49 

where  40  tons  of  manure  were  incorporated  with  the  soil  to  a 
its  maximum.  They  then  pass  through  a  minimum  thickness  of 
the  atmosphere.  At  sunrise  they  are  weakened  by  diffusion  over 
a  wide  area  and  in  addition  are  diminished  in  intensity  by  ex- 
cessive atmospheric  absorption.  The  difference  in  the  angle  of 
incidence  of  the  sun's  rays  is  the  principal  cause  of  the  difference 
between  a  tropical  climate  and  that  of  "Wisconsin.  The  slopes  on 
our  own  fields  often  offer  examples  of  such  effects.  It  is  on  a 
slope  facing  south  that  the  soil  will  reach  its  highest  temperature 
during  sunshine. 

A  dark  colored  soil  becomes  warmer  in  the  sun's  rays  than  a 
light  colored  one,  a  larger  proportion  of  the  sun's  energy  being 
absorbed  and  converted  into  heat.  No  difference  will  be  observed 
on  cloudy  days.  At  night  all  soils  will  cool  to  the  same  point. 

When  a  soil  is  freely  exposed  to  the  sky  the  temperature  at  the 
surface  will  reach  a  higher  maximum  and  fall  to  a  lower  min- 
imum than  the  air  above  it.  Schuebler  found  that  the  freely  ex- 
posed soil  in  his  garden  at  Tuebingen,  Germany,  averaged  at 
one-twelfth  inch  below  the  surface,  shortly  after  noon  and  in  per- 
fectly clear  weather,  about  120°  Fahr.  for  every  month  from 
April  to  September  inclusive,  and  in  July  reached  146° ;  this 
latter  temperature  wras  65°  above  that  of  the  air  taken  at  the 
same  time. 

With  dry  soils,  including  only  hygroscopic  water,  about  3  cubic 
feet  would  be  heated  by  the  sun  to  the  same  degree  as  one  cubic 
foot  of  water.  In  this  condition  there  is  little  difference  between 
different  soils;  a  dry  peat  will  consume  the  least  heat  and  a  dry 
clay  the  most.  When,  however,  soils  become  wet  great  differ- 
ences appear.  In  a  freshly  drained  condition,  a  coarse  gravel  or 
sand  will  warm  to  a  greater  depth,  while  soils  retaining  more 
water  will  warm  to  a  less  depth.  The  specific  heat  of  wet  peat 
does  not  differ  greatly  from  that  of  its  own  bulk  of  water. 

The  depth  to  which  a  soil  will  be  heated  depends,  however, 
partly  on  the  conductive  power  of  its  constituents.  Sand  has  the 
greatest  power  of  conducting  heat  of  any  soil  constituent.  Air, 


50  Agricultural  Chemistry. 

present  in  the  soil,  is  the  worst  conductor.  A  dry  soil  is  thus 
a  very  poor  conductor  of  heat.  Consolidation  improves  the  con- 
ductivity. Wetting  the  soil  doubles  the  conductivity  of  sand, 
limestone,  or  clay  by  displacing  the  air.  We  see  then,  that  a 
dry,  loose  soil  will  get  very  hot  at  the  surface  when  exposed  to 
the  sun,  but  the  heat  will  penetrate  to  a  slight  depth.  This  ex- 
plains why  gravelly  soils  are  best  suited  for  early  spring  crops. 

Presence  or  absence  of  much  water  is  the  important  factor 
which  chiefly  determines  the  cold  or  warm  character  of  a  soil. 
A  still  more  potent  reason  for  the  coldness  of  wet  soils,  is,  how- 
ever, the  loss  of  heat  during  evaporation.  When  a  pint  of  water 
is  removed  by  evaporation  from  97  pints,  the  96  remaining  pints 
will  have  fallen  10°  Fahr.  in  temperature  unless  this  amount  of 
heat  has  been  supplied  from  some  external  source.  Undrained 
meadows  and  heavy  clays  consequently  are  cold  soils  because 
much  of  the  sun's  heat  is,  in  these  cases,  consumed  in  evaporating 
water.  Parks  found  that  an  undrained  peat  bog  30  feet  deep, 
had  a  temperature  of  46°  when  measured  below  a  distance  of 
1  foot  from  the  surface.  In  the  middle  of  June  he  found  the 
temperature  47°  at  7  inches  below  the  surface,  while  the  drained 
portion  had  a  temperature  of  66°  at  this  depth,  and  a  tempera- 
ture of  50°  at  2  feet  below  the  surface.  Draining  is  the  only 
cure  for  a  cold,  wet  soil. 

The  temperature  of  the  subsoil  is  practically  constant  through- 
out the  year  at  a  certain  distance  from  the  surface.  Observations 
at  Greenwich  Observatory,  England,  in  a  well  drained  gravel, 
showed  that  the  variations  of  day  and  night  are  slightly  felt  at 
3  feet  from  the  surface.  At  25!/2  feet  the  maximum  temperature 
usually  occurs  in  the  latter  part  of  November  and  the  minimum 
in  the  first  week  in  June.  The  difference  between  the  two  is 
about  3°.  These  observations  make  it  clear  that  the  soil  and 
subsoil  are  generally  warmer  than  the  air  in  autumn  and  cooler 
than  the  air  in  spring. 

Tenacity  of  soil.  The  tenacity  of  a  heavy  soil  is  due  to  the 
fine  silt  and  clay.  The  coarser  elements  of  a  soil,  such  as  a  fine 


The  Soil  51 

sand,  exhibit  little  cohesion.  Clay  owes  its  cementing  power  it 
is  believed,  to  the  presence  of  a  small  quantity  of  a  hydrated  col- 
loid (jelly-like)  body,  which  according  to  Schloesing  rarely  ex- 
ceeds 1.5  per  cent  of  the  clay.  The  remainder  of  the  clay  is  com- 
posed of  extremely  fine,  solid  particles.  In  the  purest  natural 
clays,  all  the  constituents  have  the  same  general  chemical  com- 
position, that  is,  they  are  hydrated  silicates  of  aluminum ;  but  in 
soils  the  non-colloid  constituents  of  the  clay  may  be  of  a  very 
various  nature.  In  brick  clay  this  material  is  quartz  sand;  in 
marl  it  is  limestone. 

The  condition  of  clay  soils  depends  much  on  whether  the  clay 
is  coagulated  or  not.  When  the  clay  is  uncoagulated,  the  soil  is 
-sticky,  impervious  to  water,  and  cannot  be  reduced  to  a  fine  tilth. 
When  a  clay  is  coagulated  the  soil  has  a  granular  structure,  is 
pervious  to  water,  and  can  be  reduced  to  powder.  It  is  coagu- 
lated by  lime  and  by  many  salts,  and  especially  by  salts  of  cal- 
cium. Colloid  clay  will  remain  permanently  suspended  in  dis- 
tilled water.  It  is  precipitated  by  the  addition  of  a  small  quan- 
tity of  a  calcium  salt.  An  application  of  lime  to  clay  soils  is 
well  known  to  be  extremely  effective  in  diminishing  their  ten- 
acity, rendering  them  pervious  to  water,  and  more  easy  of  tillage. 

In  cultivated  sandy  soils  humates  are  often  of  great  value  as 
cementing  materials;  these,  like  true  clay,  are  colloid  bodies. 
Schloesing  found  that  1  per  cent  of  a  humate,  as  calcium  humate,. 
was  as  effective  as  a  cement  for  sand  as  11  per  cent  of  clay. 
Humates,  however,  will  lose  their  cementing  power  on  drying, 
while  clay  will  not.  The  improvement  of  the  texture  of  sandy 
soils  by  the  continued  use  of  farm  yard  manure,  or  by  the  plow- 
ing under  of  green  crops,  is  a  fact  familiar  to  the  farmer.  While 
applications  of  humus  forming  materials,  as  the  above,  increase 
the  coherence  of  sand,  they  have  an  opposite  effect  on  clay,  and 
are  the  most  effectual  means  at  the  disposal  of  the  farmer  for 
lightening  a  heavy  soil.  Lime  will  also  tend  to  increase  the  co- 
herence of  sand. 


\ 


52  Agricultural  Chemistry. 

Relation  to  water.  We  have  learned  that  a  good  soil  consists 
of  solid  particles  of  fairly  uniform  size.  The  spaces  between 
these  particles  constitute  about  40  per  cent  of  the  volume.  If 
the  particles  are  a  mixture  of  large  and  small,  as  for  example 
gravel  and  sand,  the  volume  of  these  spaces  is  much  reduced.  On 
the  other  hand  if  the  particles  are  themselves  porous,  as  in  the 
case  of  chalk,  loam,-  and  especially  humus,  then  the  volume  of 
the  spaces  is  increased.  It  is  this  volume  of  the  inter-spaces 
which  determines  the  amount  of  water  which  a  soil  will  contain 
when  perfectly  saturated,  or  the  amount  of  air  which  it  will  con- 
tain when  dry. 

Humus  increases  the  capacity  for  a  soil  to  absorb  and  retain 
water  and  consequently  a  crop  grown  on  a  soil  containing  a  fair 
amount  of  humus  is  less  likely  to  suffer  from  drought.  The  fol- 
lowing table  illustrates  this  point.  It  gives  the  amount  of  water 
held  by  1  cubic  foot  of  different  varieties  of  soil ; 

Lbs.  of  water  in 
Kind  of  Soil  1  cubic  foot 

Sand 27.3 

Sandy  Clay 38.8 

Loam 41 . 4 

Humus 50.1 

Farm  crops  will  not  grow  in  a  soil  permanently  saturated  with 
water  and  from  which  air,  consequently,  is  excluded;  the  best 
growth  is  obtained  from  soils  one-half  or  two-thirds  saturated. 
The  surface  of  a  soil  is  seldom  saturated,  except  immediately 
after  a  heavy  rain;  it  is  the  quantity  of  water  which  a  soil  will 
retain  when  fully  drained  which  determines  its  capacity  for  sup- 
plying a  crop  with  water.  The  amount  of  water  permanently 
retained  by  a  soil  does  not  depend  upon  the  volume  of  the  inter- 
spaces, but  upon  the  extent  of  internal  surface,  the  water  being 
held  by  adhesion  as  a  film  on  the  surface  of  the  particles.  The 
smaller,  therefore,  the  particles  of  a  soil,  or  the  more  porous,  the 
greater  is  the  amount  of  water  retained.  Two  samples  of  pow- 


The  Soil  53 

dered  quartz,  one  coarse,  the  other  very  fine,  will  hold  when 
saturated,  more  than  40  per  cent  of  their  volume  as  water.  But 
when  drained,  the  coarse  sand  will  retain  about  7  per  cent  while 
the  fine  quartz  holds  44.6  per  cent  of  water.  The  latter  will 
loose,  in  fact,  no  water  by  drainage. 

Gravels  and  coarse  sand  retain  the  least  water  when  drained. 
As  the  particles  become  smaller,  the  retention  of  water  increases. 
Colloids,  jelly-like  bodies,  as  clay  and  humus,  increase  the  power 
of  retaining  water,  as  such  bodies  swell  up  when  wetted  and  hold 
the  water  in  jelly-like  substances;  The  addition  of  humus  to 
soils  is  one  of  the  best  ways  of  increasing  their  water  retaining 
capacity. 

Water  from  below  may  supply  a  surface  soil  if  a  saturated  sub- 
soil exists  at  a  moderate  distance.  Such  water  is  said  to  be 
raised  by  capillary  action,  which  simply  means  that  the  surfaces 
of  the  soil  particles  exert  an  attraction  for  water.  The  finer  the 
particles  and  the  closer  they  are  packed,  the  greater  the  height  to 
which  water  will  be  carried  by  capillary  action.  When  the  dis- 
tance it  has  to  travel  increases,  the  quantity  reaching  the  surface 
diminishes.  When  the  fineness  of  the  particles  exceeds  a  certain 
point  the  quantity  of  water  raised  also  diminishes.  It  is  not 
always  the  soil  with  the  finest  particles  that  brings  most  water 
to  the  surface.  There  is  a  certain  degree  of  fineness  of  soil  par- 
ticles that  acts  most  effectively.  Capillary  action  is  seldom  able 
to  maintain  a  sufficient  water  supply  at  the  surface.  In  Wiscon- 
sin every  few  years  crops  suffer  from  drought,  although  a  per- 
manent water  supply  exists  several  feet  below  the  surface.  Cap- 
illary action  is  most  effective  in  the  case  of  silty  soils ;  such  soils 
were  deposited  from  running  water  and  consist  of  very  uniform 
particles,  but  without  any  true  clay.  Some  western  soils,  which 
are  capable  of  growing  wheat  with  a  winter  rainfall  of  10  to  12 
inches  and  a  continuous  summer  drought  of  three  months'  dura- 
tion, are  deep,  fine  grained,  and  uniform,  with  practically  no 
particles  of  the  fineness  of  clay  to  check  the  upward  lift  of 
capillarity. 


.VI  Agricultural  Chemistry. 

The  evaporation  from  a  saturated  soil  is  greater  than  from  a 
water  surface  and  as  the  soil  drys  the  rate  of  evaporation  rapidly 
diminishes.  The  average  annual  evaporation  from  a  bare  loam 
at  Madison,  Wisconsin,  is  about  fifteen  inches.  "While  soils  of 
various  character  evaporate  equal  amounts  while  saturated, 
they  exhibit  great  differences  as  drying  proceeds.  A  soil  of 
coarse  particles  and  loose  texture  dries  quickest  and  to  the 
greatest  depth.  Consequently  it  appears  to  be  good  practice 
to  avoid  deep  tillage  in  early  summer,  if  land  is  intended  to  carry 
a  crop. 

Evaporation  from  the  soil  is  diminished  by  protection  from 
sun  and  wind.  Economy  of  water  is  best  effected  by  mulching 
with  straw.  Keeping  the  surface  stirred  to  a  depth  of  an  inch 
or  two,  thus  providing  a  mulching  of  loose  dry  soil,  is  an  excel- 
lent practice  and  forms  a  fundamental  part  of  successful  culti- 
vation in  dry  climates. 

The  greatest  evaporation  of  water  takes  place  from  the  soil 
when  it  grows  a  crop.  The  water  in  a  soil  growing  barley  and 
in  an  adjacent  bare  fallow  was  determined  at  Rothamsted,  Eng- 
land, at  the  end  of  June  during  the  drought  of  1870.  It  was 
found  that  down  to  54  inches  below  the  surface  the  barley  soil 
contained  9  inches  less  water  than  the  fallow  soil.  The  injurious 
effect  of  weeds  in  the  summer  time  is  largely  due  to  their  robbing 
the  soil  of  water. 

With  dry  soils  the  farmer  should  aim  to  increase  the  amount 
of  humus.  Crops  should  be  sown  early  and  the  land  kept  solid ; 
very  shallow  summer  cultivation  should  be  resorted  to.  Such 
land  may  possess  distinct  advantages.  It  furnishes  the  earliest 
crops  to  market  gardeners,  the  soil  being  easily  wanned.  A  little 
rain  will  wet  it  to  a  considerable  depth  and  the  whole  of  the 
water  it  contains  is  available  to  plants. 

A  soil,  when  drained,  is  seldom  too  wet  because  of  its  power  to 
retain  water.  The  trouble  is  more  often  due  to  want  of  drain- 
age ;  the  remedy  for  such  a  soil  is  deep  tillage  and  draining.  Ap- 
plications of  lime  or  an  increase  in  the  humus  content  may  bo 


The  Soil  55 

an  effective  means  of  rendering  the  surface  soil  more  pervious 
to  water. 

The  wettest  soil  does  not  always  supply  the  largest  amount  of 
water  to  a  crop.  A  peaty  soil  holds  most  water,  but  it  is  held 
so  firmly  by  the  colloid  matter  as  to  be  unavailable  to  plants. 
A  stiff  clay  fails  in  a  drought  as  the  water  in  this  class  of  soils 
is  also  firmly  held  and  moves  with  difficulty.  Soils  composed  of 
silt  or  extremely  fine  sand  are  those  which  yield  water  most 
effectually  to  a  growing  crop. 

Chemical  changes  occurring  in  soils.  The  chemical  changes 
going  on  in  soil  are  numerous  and  complex.  The  mineral  matter 
is  subjected  to  the  same  influences  as  led  to  its  breaking  down  in 
the  formation  of  soil  from  the  original  rock.  These  changes  are, 
however,  hastened  because  of  the  great  quantity  of  carbon  di- 
oxide produced  by  the  decay  of  organic  matter.  Fragments  of 
feldspar  are  decomposed  with  formation  of  silicic  acid,  potassium 
carbonate  and  kaolin  or  clay.  The  clay  remains  behind,  but  the 
silicic  acid  and  potassium  carbonate  may  in  part  be  dissolved  and 
either  carried  away  in  the  drainage,  or  may  be  absorbed  by  the 
roots  of  plants  or  by  some  of  the  absorptive  constituents  of  soils. 
Calcium  carbonate  or  limestone  is  dissolved  by  water  containing 
carbon  dioxide,  which  is  true  of  all  soil  waters,  and  is  in  part 
carried  away  in  the  drain  or  absorbed  by  certain  soil  constituents. 

Calcium  phosphate,  as  it  exists  in  minerals,  is  nearly  insoluble 
in  water,  but  through  the  action  of  the  soil  water  containing 
carbon  dioxide  in  solution,  it  is  changed  to  more  soluble  forms 
and  therefore  becomes  available  to  plants.  In  contact  with  cer- 
tain forms  of  iron  and  aluminum  in  the  soil  the  soluble  calcium 
phosphates  may  be  changed  to  iron  and  aluminum  phosphates 
and  held  back  in  the  soil  in  finely  divided  condition,  and  though 
then  quite  insoluble  in  water,  may  still  be  dissolved  by  the  acid 
juices  of  the  plant's  roots. 

Absorption  of  soluble  plant  food  by  soils.  If  the  plant  food 
made  soluble  by  the  chemical  chang<  s  occurring  in  soils  were  not 


56  Agricultural  Chemistry. 

retained  by  its  absorptive  power  the  depletion  of  fertility  would 
go  on  at  a  much  more  rapid  rate  than  it  actually  does.  Most 
soils  contain  substances,  which  have  the  power  of  uniting  with 
potassium,  ammonium,  and  to  a  less  extent  with  calcium  com- 
pounds and  with  phosphates,  converting  them  into  insoluble 
forms.  If  a  solution  containing  phosphoric  acid,  potash  or  am- 
monia is  poured  upon  a  sufficiently  large  quantity  of  fertile  soil, 
the  water  which  filters  through  will  be  found  nearly  destitute  of 
these  substances.  This  retentive  power  of  a  soil  is  of  the  great- 
est agricultural  value  as  it  enables  it  to  maintain  its  fertility 
when  washed  by  rain  and  permits  of  the  economic  use  of  many 
soluble  manures.  Ferric  oxide,  a  common  ingredient  of  soil  and 
one  to  which  the  red  color  of  many  soils  is  due,  will  retain  and 
fix  any  soluble  phosphate.  When  a  solution  of  phosphate  of  cal- 
cium in  carbon  dioxide  is  placed  in  contact  with  an  excess  of 
hydrated  ferric  oxide,  the  phosphoric  acid  is  gradually  absorbed 
and  the  calcium  left  in  solution  as  a  carbonate.  Hydrated 
alumina  acts  in  the  same  way.  Ferric  oxide  and  alumina  have 
also  a  retentive  power  for  ammonia,  potash  and  other  bases,  but 
the  compounds  formed  are  more  or  less  decomposed  by  water. 

The  permanent  retentive  power  of  soils  for  potash  and  other 
bases  is  chiefly  due  to  the  hydrous  double  silicates. 

Humus  has  a  great  absorptive  power  for  ammonia.  It  also  re- 
tains other  bases  with  which  it  can  form  insoluble  compounds. 

Magnesia,  lime  and  soda  are  retained  by  the  soil,  but  in  a 
less  powerful  manner  than  are  potash  and  ammonia.  When  a 
solution  of  a  salt  of  potassium  or  ammonium  is  placed  in  contact 
with  a  fertile  soil,  lime  will  come  into  solution  and  take  the  place 
of  the  potash  or  ammonia,  which  is  by  preference,  absorbed. 

Soils  destitute  of  lime  retain  very  little  potash  or  ammonia 
when  these  are  applied  as  salts  of  powerful  acids,  as  for  instance, 
as  chlorides,  nitrates,  or  sulphates.  When  carbonate  of  calcium 
is  present  the  potassium  or  ammonium  salt  is  decomposed,  the 
base  is  retained  by  the  soil,  while  the  acid  escapes  into  the  drain- 


The  Soil.  57 

age  water  united  with  calcium.  This  is  illustrated  in  the  fol- 
lowing equation: 

Calcium  carbonate  -f-  potassium  chloride  =  calcium 

chloride  +  potassium  carbonate. 

The  addition  of  marl  or  limestone  may  thus  greatly  increase  the 
.retentive  power  of  a  soil  for  bases.  The  bases  absorbed  by  the 
soil  may  be  slowly  removed  by  the  action  of  water.  This  of 
course  occurs  to  the  least  degree  in  a  soil  that  has  absorbed  little 
or  has  been  already  washed,  and  is  greatest  in  a  soil  that  has  been 
.heavily  manured. 

The  permanent  fertility  of  a  soil  is  closely  connected  with  its 
power  of  retaining  plant  food.  In  soils  containing  clay,  only 
traces  of  phosphoric  acid,  ammonia  or  potash  are  ever  found  in 
the  drainage  water.  Sandy  soils,  from  their  smaller  chemical 
retentive  power  and  free  drainage,  are  of  less  natural  fertility 
and  much  more  dependent  on  immediate  supplies  of  plant  food. 

There  can  be  little  doubt  that  the  active  plant  food  contained 
in  a  soil,  which  is  capable  of  being  taken  up  by  roots,  exists 
either  in  solution  or  in  the  states  of  combination  just  referred 
to — that  is,  in  union  with  ferric  oxide,  hydrous  silicates  or  hu- 
mus. Different  crops  have  very  different  powers  of  attacking 
these  various  forms  of  plant  food. 

Nitrification.  Perhaps  the  most  important  reactions  going  on 
in  a  soil  are  those  connected  with  the  decay  of  organic  matter 
and  the  changes  in  the  state  of  combination  of  the  nitrogen.  The 
organic  matter  is  continually  being  oxidized,  the  carbon  being 
mainly  converted  into  carbon  dioxide.  The  material  from  which 
the  nitrogenous  matter  of  soils  is  derived  contains  always  a  large 
proportion  of  carbon.  In  the  roots  and  stubble  of  cereal  crops 
the  relation  of  nitrogen  to  carbon  is  about  1:43;  in  those  of 
leguminous  crops  1 :23 ;  in  moderately  rotted  farm  manure  1 :18. 
In  an  aerated  soil  these  materials  are  oxidized  by  the  action  of 
various  organisms  (worms,  fungi,  and  bacteria)  and  large  quan- 
tities of  carbon  dioxide  produced.  As  a  result  of  this  loss  of 
Carbon,  we  find  that  the  surface  soil  of  a  pasture  (roots  removed) 


58  Agricultural  Chemistry. 

will  contain  about  1  part  of  nitrogen  to  13  of  carbon ;  the  surface 
soil  of  an  arable  field  1:10,  and  a  clay  soil  1:6.  These  figures 
represent  the  proportion  of  nitrogen  to  carbon  in  the  commonest 
forms  of  humus  matter.  Humus  represents  merely  a  stage  in 
the  decomposition  of  organic  matter;  in  the  end  the  whole  of 
the  carbon,  hydrogen  and  nitrogen  appear  as  carbon  dioxide, 
water  and  ammonia  or  nitrates. 

The  nitrogen  contained  in  humus  is  not  in  a  condition  to  serve 
as  food  for  ordinary  crops.  The  gradual  decomposition  of  soil 
humus  is  consequently  generally  essential  to  fertility.  This 
change  in  the  humus  is  brought  about  by  fungi  and  bacteria, 
which  convert  the  nitrogen  of  organic  matter  into  ammonia  and 
nitrates,  forms  which  are  soluble  in  water  and  available  to  the 
plant.  The  final  nitrification  of  ammonia  is  performed  by  two 
species  of  bacteria,  one  of  which  produces  nitrites,  which  the 
other  changes  into  nitrates.  Fresh  plant  residues  are  more  easily 
nitrified  than  old  humus  matter,  but  nitrification  does  not  begin 
until  the  earlier  stages  of  decomposition  have  occurred. 

The  nitrifying  organisms  occur  most  abundantly  in  the  surface 
soil;  the  depth  to  which  their  action  extends  depends  on  the 
porosity  of  the  soil.  In  experiments  at  Rothamsted,  England, 
on  a  clay  subsoil,  it  was  found  that  the  organisms  did  not  always 
occur  in  samples  of  the  soil  taken  at  more  than  3  feet  below  the 
surface. 

Nitrification  only  takes  place  in  a  moist  soil  and  one  sufficiently 
porous  to  admit  air.  It  is  always  necessary  that  some  base 
should  be  present  with  which  the  nitric  acid  formed  may  com- 
bine. This  condition  is  usually  fulfilled  by  the  presence  of  car- 
bonate of  lime.  Lack  of  oxygen  and  an  acid  condition  of  the 
soil  are  both  unfavorable  to  the  growth  of  nitrifying  organisms. 
This  gives  us  a  rational  explanation  of  the  advantages  of  thor- 
ough tillage  which  aerates  the  soil  and  of  the  maintenance  of 
non-acid  soils  by  the  application  of  lime.  Nitrification  is  most 
active  in  the  summer  season;  it  ceases  near  the  freezing  point. 
The  nitrifying  organisms  may  be  killed  by  severe  drought. 


The  Soil.  59 

The  oxidation  of  humus  not  only  makes  the  nitrogen,  which 
it  contains,  available  to  plants,  but  it  also  liberates  the  ash  con- 
stituents combined  with  the  humus  and  enables  them  to  take  part 
again  in  the  nourishment  of  the  growing  crop. 

Oxidation  is  most  active  in  soils  under  tillage.  In  arable  land 
the  production  of  available  plant  food  is  at  its  maximum  and 
so  is  also  the  waste  by  drainage.  The  nitrogenous  humus  matter 
of  tilled  land  is  maintained  only  when  the  new  supply  from  crop 
residues  and  organic  manures  is  equal  to  the  amount  annually 
oxidized.  In  an  untilled  pasture  or  forest  soil,  on  the  other  hand, 
a  considerable  accumulation  of  organic  matter  may  take  place, 
the  annual  residue  of  dead  leaves  and  roots  being  often  in  excess 
of  the  amount  oxidized. 

In  a  peat  bog  oxidation  is  further  checked  by  the  high  water 
level,  which  excludes  air  from  the  soil ;  under  such  conditions  an 
unlimited  accumulation  of  organic  matter  may  take  place  if 
plants  capable  of  growing  under  these  circumstances  are  present. 

Dentrification — TVhen  a  soil  is  not  in  an  aerated  condition, 
but  has  the  spaces  between  the  particles  filled  with  water,  the 
nitrates  present  are  destroyed  by  certain  kinds  of  bacteria,  the 
oxygen  of  the  nitrate  combining  with  carbon  to  form  carbon 
dioxide,  while  the  nitrogen  is  set  free  and  returned  to  the  air 
in  its  elemental  condition.  If  a  soil  be  consolidated,  water- 
logged or  highly  charged  with  oxidizable  carbonaceous  matter, 
the  conditions  become  favorable  for  denitrification.  Conditions- 
favorable  to  nitrification,  such  as  a  plentiful  supply  of  oxygen 
and  absence  of  acidity,  are  those  unfavorable  to  denitrification, 
so  that  the  farmer  in  producing  proper  conditions  for  the  former 
desirable  process  is  at  the  same  time  preventing  the  injurious 
denitrification.  The  application  of  very  large  dressings  of 
manure,  along  with  nitrate  of  soda,  sometimes  causes  a  consid- 
erable loss  of  nitrogen  from  this  process  of  denitrification. 

Fixation  of  atmospheric  nitrogen  in  soils.  Besides  the  organ- 
isms associated  with  leguminous  plants  and  which  assimilate 
atmospheric  nitrogen  freely  when  in  union  with  the  roots  of  thi) 


60  Agricultural  Chemistry. 

liost  plant,  there  are  bacteria  in  the  soil  which  use  free  nitrogen, 
but  which  do  not  grow  in  union  with  the  higher  plants.  These 
bacteria  are  found  in  most  soils  and  are  said  to  possess  this  power 
when  the  supply  of  carbonaceous  matter  in  the  soil  is  plentiful. 
Indeed,  some  years  ago,  such  organisms  under  the  name  of 
"alinite"  were  prepared  for  sale,  but  the  success  attending  their 
use  was  doubtful  and  their  manufacture  has  ceased. 

It  is  thought  that  the  fertility  and  richness  in  nitrogen  of 
forest  or  prairie  soil  is  largely  due  to  the  activity  of  such  or- 
ganisms, which  would  find  suitable  conditions  for  growth  in  the 
large  quantity  of  organic  carbonaceous  matter  contained  in  such 
soils.  At  present  it  is  impossible  to  say  whether  the  nitrogen 
added  to  the  soil  in  this  way  is  of  any  considerable  amount. 

Gases  in  a  soil.  The  spaces  between  the  particles  of  soil,  be- 
sides containing  a  certain  amount  of  moisture,  are  usually  occu- 
pied by  air.  Because  of  the  chemical  changes  going  on  in  the 
soil  this  air  becomes  robbed  of  its  oxygen,  and  enriched  with 
carbon  dioxide.  This  air  is  not  stagnant  but  undergoes  constant 
renewal  by  diffusion  from  the  air  above. 

The  gases  drawn  from  the  soil  at  different  times  will  be  found 
to  vary  in  composition ;  the  oxygen  may  be  anywhere  from  10  to 
20  per  cent,  the  carbon  dioxide  from  1  to  10  per  cent,  while  the 
nitrogen  usually  differs  very  little  in  amount  from  that  in  the 
atmosphere,  that  is,  about  78  per  cent.  The  amount  of  carbon 
dioxide  is  greater  and  of  oxygen  less  during  the  summer  and 
autumn  than  in  the  winter  or  spring.  The  higher  temperature 
in  the  soil  during  summer  and  autumn  favors  chemical  decom- 
position, with  greater  production  of  carbon  dioxide. 

Tillage  and  drainage.  The  operations  of  tillage  and  drainage 
serve  in  many  important  ways  to  make  the  conditions  for  plant 
life  more  favorable  and  to  increase  the  amount  of  plant  food 
which  is  at  the  disposal  of  the  crop. 

By  tillage  the  surface  soil  is  pulverized  and  brought  into  a 
loose,  open  condition.  Large  lumps  are  broken  into  small  par- 
ticles and  the  fine  tilth  thus  obtained,  allows  a  rapid  extension 


The  Soil.  61 

of  the  delicate  root  fibres  and  consequently  greater  room  for  root 
growth.  It  increases  the  surface  to  which  the  roots  are  exposed 
and  necessarily  gives  the  developing  plant  a  larger  feeding  area. 

Tillage  hastens  chemical  changes  in  the  soil  by  bringing  to- 
gether particles  which  have  not  before  been  in  contact.  Par- 
ticles with  different  chemical  properties  are  thus  enabled  to  act 
upon  each  other. 

The  changes  induced  by  freezing  and  thawing  may  also  be 
greatly  increased  by  proper  tillage.  Fall  plowing  exposes  the 
large  lumps  to  the  influence  of  the  weather  during  the  winter. 
This  disintegrates  the  clods  and  improves  some  classes  of  soils 
in  a  remarkable  manner.  It  also  tends  to  save  the  moisture,  as 
the  loose  ground  turned  up  by  the  plow  prevents  loss  of  water 
by  evaporation.  The  broken  uneven  surface  also  favors  a  greater 
absorption  by  the  soil  of  the  winter  rain  or  snow.  In  an  experi- 
ment at  the  Wisconsin  Station,  a  plot  plowed  in  the  fall  con- 
tained 1.15  acre  inches  more  water  than  an  adjacent  plot  not 
so  plowed.  It  must  be  remembered  that  fall  plowing  may  not 
always  be  the  best  practice,  as  hard  soils,  low  in  humus,  may  be 
badly  puddled  if  fall  plowed.  Plowing  the  ground  very  early  in 
the  spring  is  a  rational  practice,  for  there  is  no  other  season  when 
tillage  is  so  effective  in  conserving  the  soil  moisture.  Experi- 
ments indicate  that  in  soils  where  such  practice  has  been  fol- 
lowed, the  moisture  content  will  be  greater  than  in  those  un- 
plowed.  Judgment  must  be  exercised,  however,  in  the  choice 
of  time  in  order  that  no  injury  to  the  texture  may  follow. 

By  the  action  of  the  plow,  the  residues  of  crops,  weeds  and 
manures  are  buried,  and  incorporated  with  the  soil.  The  deep 
tillage  of  heavy  land  allows  rain  to  penetrate  it  and  establishes 
the  drainage  of  the  surface  soil,  and  increases  the  temperature. 

A  shallow  surface  tillage  preserves  the  moisture  of  the  soil  in 
time  of  drought.  It  lessens  the  evaporation  from  the  surface  by 
breaking  the  capillary  connection  with  the  store  of  water  below 
the  surface.  After  a  rain  this  will  be  again  established  and 
the  cultivation  should  be  repeated  as  soon  as  possible.  Such  a 


C2  Agricultural  Chemistry. 

surface  layer  of  dry  soil  is  called  an  "earth  mulch"  and  serves 
the  same  purpose  as  a  covering  of  straw  or  like  material. 

Another  important  result  of  tillage  is  that  the  soil  is  thorough- 
ly exposed  to  the  influence  of  the  air.  The  nitrification  processes 
are  greatly  facilitated,  with  the  production  of  nitrates -and  car- 
bon dioxide.  The  disintegration  and  solution  of  mineral  par- 
ticles will  take  place  from  the  mechanical  and  chemical  actions 
brought  into  play.  It  will  also  prevent  the  formation  of  such 
compounds  as  sulphide  of  iron,  known  to  be  injurious  to  vege- 
tation. Oxygen  is  also  necessary  for  the  germination  of  seeds, 
and  the  aeration  of  soils  by  tillage  is  necessary  for  this  important 
start  in  the  plant's  development. 

By  means  of  tile  drainage  the  many  chemical  reactions  going 
on  in  a  soil  are  carried  down  to  a  greater  or  less  extent  into  the 
subsoil;  for  as  the  water  level  is  lowered  the  air  enters  from 
above  to  fill  the  spaces  in  the  soil.  By  drainage,  the  depth  to 
which  the  roots  penetrate,  and  consequently  the  extent  of  their 
feeding  ground,  is  increased.  This  helps  them  to  withstand 
drought.  They  will  not  be  so  easily  affected  by  the  extreme  dry- 
ing of  the  surface  of  the  soil  that  takes  place  in  times  of  little 
rainfall.  Roots  will  not  grow  in  the  absence  of  oxygen  and  will 
rot  as  soon  as  they  reach  a  permanent  water  level. 

In  a  water-logged  soil  denitrification  is  active  and  nitrates 
present  are  destroyed,  a  part  of  the  nitrogen  being  evolved  as 
elemental  nitrogen  and  returned  to  the  atmosphere.  The  soil 
may  in  this  way,  suffer  a  considerable  loss  of  plant  food  by  lack 
of  drainage. 

Losses  caused  by  drainage.  The  water  draining  from  land 
always  carries  with  it  dissolved  matter.  The  substances  chiefly 
removed  by  the  water  will  be  calcium  carbonate,  and  the  nitrates, 
chlorides  and  sulphates  of  calcium  and  sodium.  When  heavy 
rain  falls  these  substances  are  washed  into  the  subsoil  and  partly 
escape  by  the  nearest  outfall  into  the  springs,  brooks  and  rivers. 
The  loss  of  nitrates  during  a  wet  season  may  be  very  consider- 


The  Soil 


63 


able.     The    loss   is    greatest    from    uncropped   soil   for   several 
reasons : 

(1)  Because  of  the  greater  amount  of  drainage. 

(2)  Because  no  absorption  of  nitrates  by  the  roots  of  plants 
takes  place. 


Showing  the  dangerous  practice  of  allowing  soils  to  remain  bare  and 
exposed  to  the  washing  of  rains  (after  Vivian). 

(3)  Because  the  land,  when  free  from  crops,  dries  more  slowly 
allowing  nitrification  to  proceed  for  a  longer  time. 

The  average  loss  of  nitrogen  as  nitrates  from  uncropped  soil 
at  Rothamsted,  England,  for  20  years,  was  33.8  pounds  per  acre 
which  is  equal  to  216  pounds  of  commercial  nitrate  of  soda.  The 


64  Agricultural  Chemistry. 

loss  will  vary  greatly  with  the  nature  of  the  soil.  When  the  land 
is  under  crop  this  loss  of  nitrates  by  drainage  is  greatly  reduced, 
these  being  constantly  taken  up  by  the  roots  and  employed  as 
plant  food.  In  an  experiment  at  Grignon,  France,  the  yearly 
loss  of  nitrogen  per  acre  on  a  soil  bearing  rye  grass  was  but 
2.3  pounds. 

The  losses  of  calcium  carbonate  vary  considerably,  dependent 
upon  the  nature  of  the  soil.  From  soils  of  igneous  origin  its 
amount  has  been  estimated  at  500  pounds  per  acre  per  year, 
while  from  limestone  soils  the  loss  has  been  estimated  at  as  much 
as  2700  pounds  per  acre.  The  amount  lost  is  increased  when 
ammonium  compounds  are  used  as  fertilizer. 

The  loss  of  phosphoric  acid  is  probably  very  small,  except  in 
the  case  of  peaty  soils,  which  though  often  very  deficient  in  this 
constituent  generally  lose  much  in  the  drainage.  This  is  prob- 
ably due  to  the  presence  of  vegetable  acids  and  carbon  dioxide 
produced  by  the  decay  of  organic  matter,  which  would  intensify 
the  solvent  action  of  water.  German  experiments  report  an 
annual  loss  per  acre  of  from  about  8  pounds  for  clay  soils  to 
19.6  pounds  for  peaty  soils. 

The  loss  of  potash  is  variable,  but  small  in  amount.  From  ex- 
periments at  Rothamsted,  the  annual  losses  in  potash  per  acre 
were  found  to  vary  from  3  to  12  pounds.  The  losses  of  sulphur 
by  drainage  from  soils  may  be  considerable.  At  Rothamsted  it 
was  found  that  about  50  pounds  per  acre  per  year  of  sulphur, 
calculated  as  sulphur  trioxide,  escaped  into  the  drainage  water. 

Highly  manured  land  will  sustain  larger  absolute  losses  of 
plant  food  than  lands  in  an  average  state  of  fertility. 

Soil  as  a  source  of  plant  food.  The  proportion  of  plant  food 
present  in  soils'  is  very  small  even  when  the  soil  is  extremely 
fertile,  the  bulk  of  the  soil  serving  as  a  support  for  the  plant  and 
as  a  sponge  to  hold  the  water.  Many  chemical  analyses  of  soils 
have  been  made  and  these  show  a  considerable  variation  in  the 
composition  of  soil.  A  good  arable  loam  may  contain  0.15  per 
cent  of  total  nitrogen,  0.15  per  cent  of  total  phosphoric  acid, 


The  Soil. 


65 


0.10  per  cent  of  total  sulphur  trioxide,  and  0.2  per  cent  of  potash 
and  0.5  per  cent  of  lime,  soluble  in  hydrochloric  acid.  Much 
larger  quantities  may,  of  course,  occasionally  be  present.  Plant 
food  is  not  equally  distributed  throughout  a  soil.  If  a  soil  is 
separated  by  sifting  into  finer  and  coarser  particles,  it  will  be 
found  that  the  finer  particles  are  much  the  richer  in  plant  food. 

The  weight  of  soil  on  an  acre  of  land  is  so  large  that  even 
small  proportions  of  plant  food  may  amount  to  very  considerable 
quantities.  An  arable  loam  to  the  depth  of  1  foot  will  weigh, 
when  perfectly  dry,  about  4,000,000  pounds.  A  pasture  soil  will 
be  lighter,  the  first  foot  weighing  when  dried  with  the  roots  re- 
moved about  3,000,000  pounds.  If  such  soils  therefore  contain, 
when  dry,  0.10  per  cent  of  nitrogen,  phosphoric  acid,  potash  or 
sulphur  trioxide,  the  quantity  of  each  in  1  foot  of  soil  will  be 
from  3,000  to  4,000  pounds  per  acre. 

The  following  table,  partly  taken  from  Vivian,  gives  the  ap- 
proximate amounts  of  nitrogen,  phosphoric  acid,  potash  and  sul- 
phur trioxide  in  the  first  foot  of  typical  sandy  loam,  clay  loam 
and  clay  soils : 

Amount  of  Plant  Food  per  Acre  in  the  Surface  Foot. 


Kind  of  Soil 

Nitrogen 
Ibs. 
per  acre 

Phosphoric 
acid 
Ibs. 
per  acre 

Potash 
Ibs. 
per  acre 

Sulphur 
trioxide 
Ibs. 
per  acre 

Sandy  loam   .    .    . 

3  736 

7  326 

28  669 

4  000  (assumed) 

Clav  loam  
Clav 

4,789 
3,250 

4,935 
5  600 

44,827 
12  600 

4,000  (assumed) 
4  UOO  (assumed) 

The  amount  of  plant  food  present  in  the  soil  is  surprising,  in 
view  of  the  fact  that  it  is  often  difficult  to  maintain  a  satisfactory 
yield  of  crops.  An  acre  of  soil  may  contain  many  thousand 
pounds  of  phosphoric  acid  or  of  nitrogen  and  yet  be  in  poor  con- 
dition; while  an  application  of  commercial  fertilizer  supplying 
50  pounds  of  readily  available  phosphoric  acid  in  the  form  of 


66  Agricultural  Chemistry. 

super-phosphate  or  nitrogen  as  nitrate  of  sodium,  may  greatly 
increase  its  productiveness.  If  we  compare  the  above  table  with 
the  table  in  the  appendix,  showing  the  amount  of  plant  food  re- 
moved by  various  farm  crops,  it  will  be  seen  that  the  clay  loam 
soils  show  the  presence  of  sufficient  nitrogen  for  95  crops  of 
wheat  yielding  30  bushels  per  acre;  phosphoric  acid  for  233 
crops ;  sulphur  trioxide  for  254  crops ;  and  potash  enough  to  sup- 
ply 1555  such  crops.  There  is,  in  addition,  nearly  as  much  phos- 
phoric acid  and  potash  in  the  second  and  third  foot,  so  that  as 
far  as  the  latter  substance  is  concerned,  the  supply  seems  almost 
inexhaustible.  The  other  two  substances,  nitrogen  and  phos- 
phoric acid,  and  probably  a  third,  sulphur,  must  be  considered 
as  limited  in  quantity  in  many  of  our  soils.  In  peat  soils,  potash 
may  also  be  very  low. 

While  chemical  analysis  will  often  disclose  a  large  total  amount 
of  plant  food  sufficient  for  many  crops,  nevertheless  experience 
has  demonstrated  that  long  before  the  theoretical  number  of 
crops  have  been  produced  the  yield  will  have  decreased  so  mate- 
rially as  to  become  unprofitable. 

Available  plant  food.  Chemical  analysis  gives  the  total 
amount  of  nitrogen,  phosphoric  acid  and  potash  in  a  soil,  but 
it  does  not  indicate  what  part  of  these  materials  is  available  to 
the  plant.  It  takes  an  inventory  of  our  stock  on  hand  but  does 
not  measure  the  crop-producing  power  of  the  soil.  A  large  pro- 
portion of  this  plant  food  is  locked  up  in  insoluble  compounds,  in 
which  form  the  plant  is  unable  to  use  it.  Food  can  be  taken  up 
by  the  roots  of  plants  only  when  in  solution  or  in  a  condition 
capable  of  being  dissolved  by  contact  with  the  acid  sap  of  the 
root  hairs. 

The  agencies  operative  in  the  soil  and  which  we  have  already 
considered  are  continually  changing  these  insoluble  compounds 
to  forms  available  to  the  plant;  most  of  the  soil  ingredients  are 
in  an  insoluble  form  and  this  fact  is  really  of  the  greatest  im- 
portance, for  if  it  were  not  so  soils  would  then  lose  fertility  by 
heavy  rains.  The  unavailable  or  " potential"  plant  food  is  grad- 


The  Soil  67 

ually  being  made  available,  but  not  with  sufficient  rapidity  to 
replace  that  removed  from  the  field  at  harvest,  and  the  yield  of 
1  crop  produced  will  be  limited  by  the  element  of  this  available 
plant  food  present  in  least  quantity. 

Continuous  cropping  of  the  soil,  with  the  removal  of  every- 
thing from  the  field  results  in  the  exhaustion  of  the  plant  food 
which  has  been  rendered  available  during  the  past  ages. 


CHAPTER  IV 
NATURAL  WATERS 

Pure  Water — or  the  substance  made  of  the  two  elements  hyd- 
rogen and  oxygen — practically  never  occurs  in  Nature.  Because 
of  its  great  solvent  properties,  water  always  dissolves  certain 
quantities  of  every  substance  with  which  it  conies  in  contact. 

The  purest  form  of  natural  water  is  rain ;  however,  rain  water 
is  never  pure,  but  contains  varying  quantities  of  dissolved  mat- 
ter. The  quantity  of  dissolved  substances  will  depend  upon  the 
locality  in  which  the  rain  fell.  In  cities  and  in  the  neighborhood 
of  factories  this  will  be  larger  than  in  the  open  country.  The 
character  of  the  substances  in  solution  will  also  depend  upon  the 
locality.  The  rain  water  in  cities,  besides  containing  compounds 
of  nitrogen,  as  ammonium  nitrate,  may  be  acid.  This  is  due  to 
dissolved  sulphuric  acid,  which  had  its  origin  in  the  sulphur  di- 
oxide produced  from  burning  coal.  In  addition  to  these  sub- 
stances rain  water  contains  dissolved  gases. 

"When  it  reaches  the  earth  the  water  at  once  begins  to  dissolve 
the  substances  upon  which  it  falls.  In  regions  where  the  surface 
is  composed  of  hard,  igneous  rocks,  the  quantity  of  material  dis- 
solved is  small,  while  on  lime-stone  soils  the  amount  of  calcium 
carbonate  that  goes  into  solution  is  large. 

The  water  which  drains  away  from  a  soil,  partly  finds  its  way 
into  the  nearest  creek,  then  to  a  stream  or  river,  and  finally  to 
the  sea.  Another  portion  sinks  into  the  earth,  until  stopped  by 
some  impervious  layer  of  rock — as  shale  or  hard  pan — when  it 
accumulates  and  eventually  finds  an  outlet  at  some  lower  level 
in  the  form  of  a  spring. 

The  industrially  important  waters  may  be  classed  as  folio™ 

1.  Rain  water. 

2.  Ground  waters  furnished  by 

(a)   Springs, 


\Ynters.  li'.i 

I)'   Shallow  wells  (penetrating  but  one  geological  stra- 
tum), 

Deep  wells   (passing  through  more  than  one  such 
stratum) . 

3.  Surface  ivaters  consisting  of 

(a)  Flowing  waters  (streams). 

(b)  Still  water  (ponds,  lakes,  etc. 

4.  NM/  irnler. 

Rain  water.     The  composition  and  character  of  this  has  al- 
y  been  described  in  Chapter  II.     It  contains  very  little  min- 
•  •ral  matter  and  is  described  as  "soft"  for  this  very  reason.     If  it 
••ould  be  collected  without  further  contamination  it  would  be  by 
far  the  best  for  most  purposes.     The  acidity  of  the  rain  in  dis- 
3  where  much  coal  is  burned  is  of  great  importance  as  affect- 
lie  growth  of  plants,  particularly  grasses  and  certain  trees. 
In  addition  to  its  direct  injurious  effect  upon  the  foliage,   it 
a  a  deleterious  action  upon  the  soil,  tending  to  remove  the 
••alrium  carbonate  or  other  basic  material  and  to  promote  "sour- 
a  condition  which  is  very  unfavorable  to  the  growth  of 
useful  plants.     It  is  known  that  grass  lands  under  such 
Distances  become  almost  sterile,  the  last  plants  to 'succumb 
.<•   unfavorable   conditions   being  usually   the  "sorrel"   or 

!  dock.'' 

Ground  Water.     The  water  issuing  from  springs  varies  great- 
ly in  the  amount  and  nature  of  the  dissolved  matter  whiclj  it  con- 
tains,    If  this  be  small,  and  not  possessed  of  strong  odor,  or  taste, 
ater  is  described  as  fresh  water;  but  if  a  large  quantity  of 
v«-d  matter  be  present,  or  if  the  water  possesses  pronounced 
"doi-.  or  medicinal  properties,  it  is  known   as  a  mineral 

Many  spring  waters  contain  the  following  substances,  but  in 
varying  amounts: 

Calcium  and  magnesium  carbonates  dissolved  in  excess 
"f  carbon  dioxide. 

Calcium  or  magnesium  sulphate. 


70  Agricultural  Chemistry. 

3.  Sodium  or  potassium  chloride. 

4.  Alkaline  silicates. 

5.  Dissolved  gases  as  oxygen,  nitrogen  and  especially  carbon 
dioxide. 

Calcium  and  magnesium  carbonates  are  almost  insoluble  in 
water,  but  if  the  water  contains  carbon  dioxide,  the  readily  sol- 
uble bi-carbonates  of  calcium  and  magnesium  are  formed. 

Such  action  occurs  in  all  lime-stone  districts  and  the  removal 
of  the  rock  by  solution  gives  rise  to  the  caves  and  underground 
water  courses  so  common  in  such  localities.  The  great  Mammoth 
Cave  of  Kentucky  and  Perry  Cave  of  Northern  Ohio  are  illus- 
trations of  such  action. 

When  such  water  is  boiled  the  bi-carbonates  are  decomposed, 
losing  part  of  their  carbon  dioxide,  and  normal  carbonates  are 
again  formed.  These  are  insoluble  and  consequently  appear  as 
a  precipitate.  In  many  cases  the  precipitated  calcium  or  mag- 
nesium carbonate  forms  a  firmly  adherent  coating  or  crust  upon 
the  bottom  or  sides  of  the  kettle  or  boiler. 

Calcium  and  magnesium  sulphates  are  soluble  in  water,  the 
former  to  the  extent  of  about  1.7  grams  per  liter  (1  oz.  in  18 
quarts  of  water).  Waters  containing  calcium  or  magnesium 
compounds  are  known  as  "hard"  waters,  and  have  a  peculiar 
and  well  known  action  on  soap.  The  latter  is  essentially  a  sodium 
salt  of  the  fatty  acids,  as  stearic,  palmitic  and  oleic  acids.  These 
acids  are  the  constituents  of  our  principal  fats  and  it  is  the  com-  j 
mon  practice  of  every  good  housewife  to  save  the  fat  "scraps'7 
for  the  home  soap-making.  The  sodium  and  potassium  salts  of 
the  fatty  acids  are  soluble  in  water,  but  the  calcium  and  mag- 
nesium salts  are  insoluble.  For  water  to  form  a  lather  with 
soap  or  properly  exercise  its  cleansing  power,  it  is  necessary  that 
the  water  should  contain  in  solution  some  of  the  sodium  or  potas- 
sium salts  of  the  fatty  acids.  When  a  small  quantity  of  soap  is 
dissolved  in  hard  water,  the  calcium  or  magnesium  present  in 
the  water  displaces  the  sodium  or  potassium  and  gives  a  curdy, 
flocculent  precipitate  of  the  calcium  or  magnesium  salts  of  the 


Natural  Waters.  71 

fatty  acids.  The  dissolved  soap  is  thus  removed  and  more  has 
to  be  dissolved  before  the  proper  cleansing  action  can  be  exerted. 
Hence  hard  waters  are  unsuitable  for  domestic,  especially  for 
laundry,  purposes ;  they  involve  the  consumption  of  large  quan- 
tities of  soap  and  contaminate  the  washed  articles  with  the  pre- 
cipitated "lime"  or  "magnesia  soap." 

Hard  waters  are  also  unsuitable  for  steam-raising,  since  the 
deposit  of  calcium  carbonate  or  calcium  sulphate  (boiler  scale) 
upon  the  boiler  plates  greatly  increases  the  consumption  of  fuel 
required  for  the  production  of  a  certain  quantity  of  steam.  Cal- 
cium carbonate  alone  forms  a  porous  and  non-adherent  scale, 
which  is  easily  removed  by  "blowing  off"  the  boiler.  Calcium 
sulphate  forms  a  hard  compact  scale,  which  adheres  very  firmly. 

A  distinction  is  often  made  between  waters,  which  contain 
their  calcium  and  magnesium  as  bi-carbonates  and  those  in  which 
the  salts  present  are  as  sulphates.  The  former  are  known  as 
"temporarily"  the  latter  as  "permanently"  hard  waters.  By 
the  removal  of  the  excess  of  carbon  dioxide  from  the  former  the 
calcium  and  magnesium  carbonates  are  precipitated,  while  with 
the  latter  the  salts  are  in  solution  and  cannot  be  precipitated  by 
the  simple  removal  of  carbon  dioxide. 

The  usual  method  of  procedure  to  effect  the  softening  of  tem- 
porarily hard  water  is  to  add  "milk  of  lime"  in  sufficient  quan- 
tity to  combine  with  the  free  carbon  dioxide  and  that  present  as 
bi-carbonates.  The  precipitate  formed  will  be  found  to  contain 
the  calcium  and  magnesium  carbonates  originally  present,  to- 
gether with  that  formed  from  the  added  lime.  On  standing,  the 
precipitate  settles  out  and  the  clear  liquid  is  then  almost  free 
from  calcium  and  magnesium  and  is  "soft."  The  milk  of  lime 
should  be  added  slowly  and  gradually  and  care  be  taken  that  no 
great  excess  is  used.  Water  so  treated  is  much  improved  both 
for  washing  and  for  steam-raising  purposes.  The  "milk  of 
lime"  is  made  by  treating  a  quantity  of  quick  lime  with  water 
and  after  thoroughly  stirring,  the  ' '  milk ' '  is  then  mixed  with  the 
water  to  be  purified. 


72  Agricultural  Chemistry. 

Another  method  is  to  boil  the  water  either  in  the  open  air  or 
in  special  heaters.  This  decomposes  the  bi-carbonates,  drives 
out  the  excess  of  carbon  dioxide  and  the  normal  carbonates  of 
magnesium  and  calcium  settle  out  as  precipitates. 

Permanent  hardness  is  less  easily  remedied,  for  in  every  case 
the  treatment  of  the  water  leaves  in  solution  some  substance  more 
or  less  deleterious.  Sodium  carbonate  and  barium  chloride  are 
the  materials  in  common  use.  A  recent  suggestion  calls  for  the 
use  of  sodium  bi-chromate  within  the  boiler,  as  a  corrective  for 
both  temporary  and  permanent  hardness.  It  is  claimed  that  the 
calcium  and  magnesium  chromates  precipitate  in  the  boiler  as  a 
loose,  non-adherent  mass,  which  is  removed  by  "blowing  off" 
daily.  It  is  further  claimed  that  the  free  chromic  acid  does  not 
attack  the  boiler  iron.  Much  care  is  necessary  in  order  to  avoid 
an  excess  of  any  chemical  added.  As  a  rule  the  water  should 
be  treated  before  it  goes  into  the  boiler.  But  if  the  scale-forming 
material  does  not  exceed  150  parts  per  million,  the  purification 
may  be  done  in  the  boiler  itself,  followed  by  daily  "blowing  off." 

A  great  many  proprietary  "anti-scale"  preparations  are  sold, 
many  of  which  are  of  no  particular  value.  Most  of  them  are  to 
be  used  inside  the  boilers.  Some  are  supposed  to  act  chemically 
on  the  impurities  and  others  are  mechanical,  preventing  the  ad- 
herence of  scale.  The  former  usually  contain  soda-ash,  caustic 
soda,  barium  hydroxide,  or  sodium  phosphate.  Tannin  in  the 
form  of  sodium  tannate,  is  sometimes  employed,  by  which  the 
calcium  and  magnesium  are  separated  as  tannates. 

In  a  drinking  water  the  presence  of  calcium  compounds,  except 
perhaps  in  excessive  amounts,  is  not  objectionable.  Indeed,  it  is 
often  advantageous,  furnishing  a  portion  of  the  lime  necessary 
for  the  building  up  of  the  hard  parts,  such  as  bones  or  shells,  of 
the  animal.  Moreover,  in  many  cases  water  is  delivered  through 
lead  pipes  and  soft  waters,  especially  if  they  contain  vegetable 
acids,  as  for  example  peaty  waters,  attack  and  dissolve  the  lead, 
and  often  to  such  an  extent  as  to  cause  lead  poisoning  in  those 


Natural  Waters.  73 

who  drink  them.  The  presence  of  calcium  sulphate  renders  wa- 
ter incapable  of  this  dangerous  action  upon  the  lead.  In  the 
presence  of  calcium  sulphate  the  metal  becomes  coated  with  a 
film  of  the  very  insoluble  lead  sulphate,  which  protects  it  from 
further  contact  with  the  water. 

Organic  matter.  Of  greater  importance  than  the  mineral  mat- 
ter in  drinking  water,  is  the  amount  and  nature  of  the  organic 
matter.  This  in  itself  is  comparatively  harmless.  Its  import- 
ance lies  in  the  influence  it  may  have  upon  the  kinds  of  micro- 
organisms which  accompany  it.  Animal  excreta  is  the  most  dan- 
gerous contamination,  since  the  micro-organisms  which  cause 
various  diseases,  as  for  example,  typhoid,  cholera,  etc.,  are  liable 
to  be  thus  introduced  into  the  water.  Animal  organic  matter  is 
richer  in  nitrogen  than  most  vegetable  refuse,  so  that  in  practice 
the  detection  of  much  combined  nitrogen,  whether  as  organic 
matter,  ammonium  salts,  or  nitrates,  is  regarded  as  sufficient  to 
indicate  that  the  water  has  been  contaminated  with  sewage  or 
other  animal  matter.  If  much  organic  matter  of  animal  origin 
be  present  there  must  always  be  considerable  risk  of  disease  pro- 
ducing organisms  finding  their  way  into  the  bodies  of  those  who 
drink  it ;  and  though  such  contaminated  water  may  be,  and  often 
is,  drunk  for  years  with  impunity,  its  consumption  is  decidedly 
dangerous. 

Another  substance  characteristic  of  sewage  is  common  salt; 
consequently  the  presence  of  much  chlorine  in  a  water  is  gen- 
erally indicative  of  sewage  contamination,  unless  the  water  is 
derived  from  some  rock  which  contains  salt,  or  is  collected  near 
the  sea. 

What  has  been  said  has  an  important  bearing  upon  the  loca- 
tion of  the  farm  wells.  Dangers  of  seepage  from  the  out  door 
privy  and  the  barn-yard  must  be  avoided  by  locating  the  well 
at  a  proper  distance  from  both  and  on  higher  ground.  Even 
these  precautions  may  not  always  entirely  remove  the  danger  of 
contamination. 


74 


Agricultural  Chemistry. 


Analyses,  quoted  from  Ingle,  of  typically  good  and  bad  drink- 
ing waters,  are  given  below. 

Composition  of  Good  and  Bad  Drinking  Waters. 


Constituents 

Good  water 
Parts  per  million 

Bad  water 
Parts  per  million 

Total  solids  

03 

530 

Nitr  ogen  as  nitrites  and  nitrates  
Free  ammonia  

0.25 
0  03 

7.8 
4.3 

Albuminoid  ammonia. 

0  07 

0.9 

Chlorine        

11.4 

69 

Tern   hardness  

1.4 

102.9 

Per.  hardness 

34  3 

205.9 

Total  hardness. 

35.7 

308.8 

By  hardness  is  meant  the  parts  of  calcium  carbonate  equivalent 
to  the  total  amount  of  calcium  and  magnesium  salts  present  in 
one  million  parts  of  the  water. 

By  albuminoid  ammonia  in  the  above  table  is  meant  the  quan- 
tity of  ammonia,  which  is  evolved  from  the  water  by  the  decom- 
position of  organic  nitrogenous  substances  when  distilled  with 
an  alkaline  solution  of  potassium  permanganate. 

Surface  water.  Rivers,  ponds  and  lakes  belong  to  this  class. 
Most  rivers  originate  in  springs,  so  at  first  their  water  resembles 
that  of  their  source.  A  considerable  influx  of  surface  water, 
however,  generally  enters  the  river  and  alters  its  composition. 
The  composition  of  the  waters  of  ponds  or  lakes  will  be  much  like 
that  of  the  creeks  and  rivers  flowing  into  them.  The  surface 
water  usually  contains  less  dissolved  matter  than  spring  water, 
but  often  more  organic  matter  and  suspended  particles.  The 
composition  of  the  river  water  depends  greatly  upon  the  char- 
acter of  the  rocks  from  which  it  is  collected.  When  the  surface 
consists  of  igneous  rocks  or  of  sandstone,  the  water  is  usually 
soft,  while  in  lime  stone  districts  it  will  be  hard.  Some  rivers, 
as  for  example  the  Trent  of  England,  are  rich  in  calcium  sul- 
phate and  to  this  fact  the  excellence  of  the  Burton  ales  has  been 


Natural  Waters. 


75 


ascribed.  The  remarkable  softness  of  the  river  Dee,  which  flows 
through  the  granite  district  of  Aberdeenshire,  England,  has  also 
received  special  notice. 

The  following  table  represents  the  average  composition  of  sev- 
eral well  known  lake  waters  of  Wisconsin. 

Composition  of  Wisconsin  Lake  Water*. 


Parts  per  Million 

Lake  Mendota 

North  Lake 

Devil's  Lake 

Silica  

1.1 

3.0 

2.2 

Alumina  and  Iron.  .  .  . 
Lime  

0.8 
40  1 

0.6 
66.2 

0.6 
4.5 

Matjii6sia 

42  3 

46  4 

1  8 

Sulphur  trioxide  
Chlorine  

10.3 
2.0 

11.1 
4.0 

6.7 

8.2 

The  softness  of  the  water  of  Devil 's  lake  is  also  to  be  attributed 
to  the  fact  that  it  is  located  in  a  sandstone  country. 

River  water  rarely  contains  large  quantities  of  calcium  car- 
bonate such  as  occur  in  some  springs,  since,  owing  to  the  free 
contact  with  air  it  never  retains  very  large  quantities  of  dissolved 
carbon  dioxide.  Calcium  sulphate  in  river  water  is  usually  ac- 
companied by  sodium  chloride  and  magnesium  salts. 

In  thickly  populated  and  manufacturing  centers  the  rivers  are 
contaminated  with  the  sewage  and  trade  effluent  of  the  towns 
and  villages,  and  thus  often  become  foul  and  bad-smelling.  This 
is  to  be  deplored  both  on  account  of  the  annoyance  and  injury 
to  health  which  they  cause,  and  also  because  of  the  serious  loss 
to  the  community  of  the  valuable  combined  nitrogen  and  other 
manurial  constituents  contained  in  the  sewage.  It  is  estimated 
that  the  Mississippi  river  carries  daily  to  the  sea  50  to  100  tons  of 
nitrogen  as  nitrates.  In  some  cities  of  America,  as  well  as  in 
Europe,  the  sewage  is  pumped  directly  to  nearby  lands  called 
"sewage  farms."  where  it  is  allowed  to  run  at  intervals  between 


76  Agricultural  Chemistry. 

thrown-up  earth  ridges.  On  these  ridges  various  crops,  especially 
vegetables,  are  grown,  with  the  resultant  utilization  of  the 
manurial  constituents  of  the  sewage. 

The  amount  of  suspended  matter  in  river  water  varies  enor- 
mously, depending  upon  the  rain  fall,  the  character  of  the  sur- 
rounding soil,  and  other  circumstances.  Soft  waters  or  those  con- 
taining carbonate  of  soda,  are  often  muddy,  while  hard  waters 
tend  to  deposit  their  suspended  clay  and  become  clear.  In  some 
cases  the  quantity  of  suspended  matter  is  very  great,  and  a  dense 
muddy  river,  if  it  over-flows  its  banks,  deposits  upon  the  soil 
a  layer  of  finely  divided  particles  of  materials  brought  down 
from  higher  up  the  valley.  The  sediment  is  often  rich  in  plant 
food  and  forms  an  important  fertilizer.  In  some  places  in  Eng- 
land, land  is  systematically  treated  with  the  flood  water  in  order 
to  increase  the  thickness  of  the  soil.  The  process  is  known  as 
"warping"  and  the  "warp"  soils  are  extremely  rich  and  fertile. 
The  Nile  river  in  Egypt  affords,  on  a  large  scale,  a  still  better 
example  of  a  river  used  in  this  manner. 

In  countries  of  limited  or  unevenly  distributed  rainfall,  as  in 
many  of  our  western  states,  irrigation  is  often  practiced.  In 
this  case,  since  there  is  very  little  drainage,  the  composition  of 
the  water  used  is  of  importance.  If  the  water  is  charged  with 
common  salt,  sodium  sulphate  or  sodium  carbonate,  there  is  grave 
danger  of  the  surface  soil,  through  the  prolonged  evaporation 
and  concentration  of  the  water,  becoming  charged  with  the  sol- 
uble matter  to  such  an  extent  as  to  seriously  interfere  with  plant 
growth.  The  soil  is  then  said  to  become  "alkali."  This  con- 
dition may  also  arise  from  accumulation-in-place  of  the  salts, 
produced  by  the  weathering  of  the  rocks.  The  slight  rain  fall  is 
insufficient  to  produce  percolation  through  the  soil  arid  carry 
the  accumulating  salts  into  the  under  ground  water  system.  This 
produces  3  sterile  condition  which  may  be  caused  by  sodium 
sulphate  and  chloride  (white  alkali),  or  by  sodium  carbonate 
(black  alkali). 


Natural  Waters. 


77 


Different  crops  are  possessed  of  different  resisting  powers  to 
these  salts.  As  a  rule  sodium  carbonate  is  the  most  effective  in 
causing  injury  to  plants  and  sodium  sulphate  the  least.  For- 
tunately, however,  " black  alkali" — i.  e.,  sodium  carbonate — can 
be  rendered  almost  harmless  by  the  application  of  gypstim  to  the 
soil,  which  decomposes  the  sodium  carbonate  with  formation  of 
the  very  much  less  harmful  substances,  sodium  sulphate  and 
calcium  carbonate.  If  "white  alkali"  is  due  to  common  salt,  it 
cannot  be  cured  except  by  drainage. 

According  to  results  accumulated  in  this  country,  and  tabu- 
lated by  Ingle,  the  following  figures  give  the  highest  proportion 
of  sodium  chloride,  sodium  sulphate  and  sodium  carbonate  which 
may  be  present  in  soils  without  injury  to  the  plants  named.  The 
figures  represent  the  amounts  in  pounds  of  the  various  constit- 
uents present  in  the  upper  four  feet  of  soil  per  acre : 


Plant 

Sodium 
Chloride 

Sodium 
Sulphate 

Sodium 
Carbonate 

Grape       .       .... 

800 

40,  800 

7,550 

Fie 

9,  640 

24,480 

1,120 

Orange. 

3,360 

18,  000 

3,840 

Apple.      ...                     .  .  • 

1,240 

14,  240 

640 

Peach  

1,000 

9,600 

680 

Oriental  sycamore 

20,  320 

19,240 

3,  200 

Salt  hush 

12,520 

125,640 

18,560 

Alfalfa    old 

5,  760 

1*'2,480 

2.360 

Su^ar  beet 

5,440 

52,  640 

4,000 

R'dish 

2,240 

51,880 

8,720 

Wheat 

1,160 

15,120 

1,480 

Barlev 

5,  100 

12,020 

12,170 

Sorghum 

9,680 

61,840 

9,840 

In  this  table  it  is  assumed  that  the  weight  of  soil  to  a  depth 
of  four  feet  per  acre  is  16,000,000  pounds,  or  that  each  acre-foot 
of  soil  weighs  4,000,000  pounds.  One  per  cent  of  any  constituent 
would  then  correspond  to  40,000  pounds  per  acre  to  a  depth  of 
one  foot,  one-tenth  per  cent  to  4,000  pounds,  and  so  on. 


78 


Agricultural  Chemistry. 


Sea  water  varies  in  composition,  dependent  upon  the  locality 
at  which  it  is  taken.  Its  composition  is  affected  by  the  influx 
of  fresh  water  from  large  rivers,  etc.,  but  far  out  from  land  it 
is  very  constant  in  composition.  The  average  amount  of  total 
solid  matter  is  about  34,000  parts  per  million.  Thorpe,  in  1870, 
found  in  the  water  of  the  Irish  sea  the  following  constituents 
expressed  in  parts  per  million : 


Sodium  chloride 26,439 

Potassium  chloride 746 

Magnesium  chloride 3,150 

Magnesium  bromide 71 

Magnesium  sulphate 2,066 

Magnesium  carbonate Trace 


Magnesium   nitrate 2 

Calcium  sulphate 1,332 

Calcium  carbonate 48 

Ammonium  chloride 0-4 

Ferrous  carbonate 5 

Silicic  acid. .                    ...  Trace 


In  certain  lakes  having  no  connection  with  the  ocean,  the  con- 
centration of  the  water  becomes  much  greater,  and  the  total  solid 
matter  may  reach  even  seven  or  eight  times  that  found  in  the 
ocean.  Examples  of  such  water  are  found  in  the  Dead  Sea  and 
the  Great  Salt  Lake  of  Utah. 


CHAPTER  V 
THE  PLANT 

The  growth  of  plants  is  the  result  of  a  series  of  chemical 
changes  which  first  assume  prominence  in  the  sprouting  seed, 
with  the  ultimate  object  of  producing  seed  for  a  succeeding  gen- 
eration. The  effects  of  these  changes  become  inconspicuous  in 
resting  seeds,  but  their  activity  ceases  only  with  the  death  of  the 
organism. 

Germination.  A  seed  is  essentially  an  embryonic  plant  sur- 
rounded and  protected  by  a  supply  of  reserve  materials  which 
serve  as  food  until  the  young  plant  can  forage  for  itself.  These 
reserve  compounds  are  more  or  less  complex  structures  involving 
simple  plant-food  constituents  derived  from  the  air  and  soil. 
The  changes  by  which  they  are  altered  for  the  use  of  the  seedling 
are  produced  by  sensitive  compounds  known  as  enzymes. 

These  compounds  are  not  endowed  with  life,  but  they  are 
probably  closely  related  in  composition  to  the  complex,  nitro- 
genous compounds  known  as  proteins,  which  form  the  basis 
of  living  matter,  and  with  whose  chemical  changes  the  life  pro- 
cesses of  plants  and  animals  appear  to  be  very  closely  connected. 
The  exact  nature  of  enzyme  action  is  not  known.  One  of  the 
older  and  more  prominent  theories  of  this  action  was  based  upon 
the  sensitiveness  of  these  bodies  and  their  proneness  to  undergo 
decomposition.  It  attributed  their  effects  to  a  sympathetic  rela- 
tion whereby  they  induced  instability,  or  accentuated  conditions 
already  unstable,  in  certain  other  compounds  and  caused  them 
to  break  down.  This  theory  is  insufficient  for  we  now  know  that 
enzymes  can  effect  the  construction,  as  well  as  the  destruction,  of 
some  compounds.  Under  proper  conditions  of  temperature  and 
moisture  small  amounts  of  a  given  enzyme  induce  changes  in  a 
large  amount  of  matter,  each  kind  of  enzyme  acting  upon  a 
specific  compound  or  group  of  compounds.  Thus,  a  specific  type 


SO  Agricultural  Chemistry. 

of  enzymes,  designated  as  proteolytic  in  nature,  alters  the  protein 
compounds  of  the  germinating  seed ;  an  enzyme  known  as  diastase 
converts  starch  to  dextrines  and  sugar;  a  lipase  or  fat  splitting 
enzyme  alters  fats  only,  while  still  another  type  of  enzyme  lib-i] 
erates  phosphorus,  calcium  and  other  ash  constituents  from  or- 
ganic compounds  of  the  seed.  Phytase,  which  occurs  in  wheat 
arid  other  grains,  is  an  example  of  the  last  mentioned  class  of 
enzymes.  It  breaks  up  the  compound  known  as  phytin,  produc- 
ing simple  soluble  compounds  of  calcium,  magnesium,  potassium 
and  phosphorus. 

Consideration  of  this  specific  relation  between  enzymes  and 
organic  compounds  and  extension  of  our  knowledge  concerning 
the  chemical  structure  of  the  substances  involved  therein  have 
led  to  a  theory  which  likens  the  action  of  an  enzyme  to  that 
of  a  key  upon  a  lock,  in  the  sense  that  each  key  fits  and  trips 
only  the  particular  lock  to  which  it  is  adapted.  This  is  more 
complete  than  the  older  theory,  for  it  ascribes  to  the  enzyme 
power  to  reconstruct  its  specific  compound  just  as  the  key  can 
lock  as  well  as  unlock.  It  is  in  harmony  with  the  known  re-j 
versibility  of  some  enzyme  actions. 

The  fragments  of  compounds  resulting  from  enzymatic  action 
in  the  seed,  combine  with  the  oxygen  of  the  air,  always  required 
for  germination,  and  either  yield  energy  for  the  growth  of  the 
young  plant,  or  pass  as  soluble  compounds  with  the  sap  into  the 
growing  seedling,  there  to  be  reconstructed  into  compounds  form- 
ing the  tissues  of  the  young  plant. 

By  the  time  the  reserve  compounds  of  the  seed  are  exhausted 
the  young  plant  is  differentiated  into  separate  organs,  known  as ! 
ro-ot,  stem  and  leaf,  by  means  of  which  it  can  assimilate  raw  food 
materials  from  the  air  and  soil. 

Functions  of  the  root.  The  root  is  an  organ  of  great  impor- 
tance in  the  assimilation  of  food.  Large  amounts  of  water  re- 
quired by  the  growing  plant,  are  taken  from  the  soil  by  means 
of  the  root  and  it  is  through  this  means  that  the  plant  obtains 
its  nitrogen  and  ash  constituents. 


The  Pl<mt.  81 

The  activity  of  this  organ  in  this  connection  is  shown  by  the 
following  figures  quoted  from  King.  The  table  expresses  the 
pounds  of  water  required  to  produce  1  pound  of  dry  substance  in 
the  plant. 

Pounds  of  Water  Required  to  Produce  One  Pound  of  Dry  Substance. 

Kind  of  Plant  Pounds  of  Water 

Dent  Corn 309 .8 

Barley . 392.9 

Oats 522.4 

Red  Clover 452.8 

Field  Peas 477.4 

Potatoes 422.7 

When  we  consider  that  field  crops  require  an  amount  of  water 
from  three  hundred  to  five  hundred  times  as  great  as  their  own 
dry  weight,  and  that  all  of  their  nitrogen  (except  in  the  case  of 
leguminous  plants)  and  all  of  their  ash  constituents  are  derived 
from  the  soil  with  this  supply  of  water,  the  great  importance  of 


Showing  the  power  of  the  rutabaga  to  obtain  its  phosphorus  from  insol- 
uble phosphates. 

Box.  1.     Soluble  phosphoric  acid. 
Box  2.     Insoluble  phosphoric  acid — Florida  rock. 
Box  3.     Insoluble  phosphates  of  iron  and  aluminum. 
Box  4.     No  phosphate  added. 


82 


Agricultural  Chemistry. 


the  function  of  assimilation  performed  by  the   roots  becomes 
evident. 

While  some  plants,  as  for  example,  tobacco  and  the  potato,  re- 
quire liberal  supplies  of  plant  food  in  readily  available  form, 
others,  especially  the  cruciferae  (turnip,  rutabaga  and  related 
plants)  and  some  of  the  gramineae  (cereal  grains  and  grasses), 
display  marked  ability  to  attack  resistant  compounds  in  the  soil 
and  obtain  food  from  them.  This  difference  is  well  illustrated 
by  the  following  data  obtained  by  Merrill  at  the  Maine  Experi- 
ment Station  in  studying  the  availability  of  phosphorus,  when 
supplied  in  various  forms  to  different  crops.  Other  requirements 
of  the  plants  than  that  for  phosphorus  were  amply  supplied. 
The  figures  express  the  percentage  yield  of  dry  matter,  the  yield 
with  no  phosphorus  being  taken  as  100  per  cent: 


Phos- 

Phos- 

Phos- 

No 

phorus 

phorus 

phorus 

Plant  Family 

Crop 

Phos- 

in ground 

in  iron  and 

in  water 

phorus 

Florida 

aluminum 

soluble 

rock 

phosphate 

forms 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Leguminosae 

Peas 

100 

140  4 

108  6 

191  8 

Clover  

100 

205.1 

152.4 

262.2 

Graminae  

Barley  

100 

117.7 

128.1 

232.5 

Corn  

100 

273.6 

316.6 

704.2 

Solonaceae  

Potato    .  .  . 

100 

114.1 

121.6 

161.2 

Tomato  

100 

255.7 

218.8 

376.1 

Cruciferae  

Turnip  

100 

159.0 

204.2 

226.6 

Rutabaga  .  .  . 

100 

286.0 

216.6 

378.1 

These  data  show  a  widely  variant  power  on  the  part  of  plants 
to  assimilate  comparatively  insoluble  and  unavailable  compounds 
of  phosphorus.  The  great  superiority  of  corn  over  barley  and 
of  the  tomato  over  the  potato  in  utilizing  the  insoluble  phosphates 
is  interesting  as  a  demonstration  that  assimilating  power  is  not 
uniform  for  members  of  a  plant  family,  but  is  a  characteristic 
of  the  individual  species.  The  cruciferae,  however,  as  a  family. 


The  Plant.  83 

are  notably  efficient  as  phosphorus  gatherers,  while  the  grass 
family  is  characterized  by  high  assimilation  of  silicon. 

The  well  known  power  of  roots  to  etch  the  surface  of  lime- 
stone is  due  to  excretion  of  carbon  dioxide  from  this  organ  of  the 
plant,  and  differences  in  ability  to  assimilate  food  materials  may 
be  explained  partly  by  differences  in  carbon  dioxide  output. 

If  the  stem  of  an  actively  growing  plant  be  severed  at  its  junc- 
tion with  the  root  and  replaced  by  a  pressure  gauge,  it  will  be 
found  that  the  root  exerts  an  upward  pressure  amounting  in  some 
cases  to  more  than  30  pounds  per  square  inch.  According  to 
Wieler  this  pressure  has  been  found  sufficient  to  support  a  column 
of  water  of  the  following  heights  in  the  plants  indicated : 

Height  of  water  column 
Plant  supported  by  root  pressure 

White  Mulberry 6.5  inches 

k     European  Ash 11.4       " 
Castor  Oil  Plant 181 .3       " 
Stinging  Nettle 249.7 
Wine  Grape 581.6      " 
White  Birch 755.0 
Sweet  Birch  (Black  Birch) 1043.2       " 

By  this  so-called  "root  pressure"  the  root  is  believed  to  func- 
tion in  the  movement  of  water  through  the  plant. 

In  biennial  root  crops  such  as  the  beet,  the  root  of  the  first 
year's  growth  serves  as  a  magazine  for  food  from  which  the 
second  year's  growth  is  re-inforced  for  the  production  of  seed. 
This  reinforcing  material  is  usually  starch  or  sugar,  with  small 
amounts  of  nitrogen  compounds  and  ash  constituents. 

The  stem.  The  active  portion  of  the  stems  of  plants  consists 
essentially  of  a  system  of  tubes  formed  by  continuously  connected 
cells.  These  tubes  serve  as  channels  for  the  transportation  of 
water  and  food  materials  and  are  surrounded  by  protecting  and 
supporting  tissue.  In  the  stems  of  endogenous  plants,  as  in  the 
corn  and  the  bamboo,  the  tough,  smooth  bark  is  formed  by  ag- 
gregates of  the  dead  remains  of  conducting  cells  and  newer 
growths  are  added  by  increments  of  these  cejls  in  the  soft  pith 


84:  Agricultural  Chemistry. 

toward  the  center  of  the  stem.  Groups  of  these  cells,  which 
traverse  the  pith  of  the  stalk  longitudinally,  are  familiarly  known 
as  the  fiber  of  hemp  and  the  threads  of  the  corn  stalk.  The 
stems  of  exogenous  plants  like  the  oak  and  maple,  which  produce 
new  tissue  outward  from  a  compact,  central  heart- wood,  consist 
of  a  tough,  supportive  core  of  the  older  and  denser  tissue  sur- 
rounded by  the  growing  cambium  layer.  This  whole  structure  is 
surrounded  and  protected  by  a  layer  of  dead  cells  forming  the 
outer  bark.  Sap  is  conveyed  about  these  plants  through  channels 
in  the  cambium  layer  or  inner  bark,  and  may  be  obtained  in 
quantity  from  some  trees,  as  from  the  sugar-maple,  by  tapping 
into  the  inner  bark  and  contiguous  woody  tissue  in  early  spring, 
when  the  rapidly  developing  buds  are  drawing  upon  reserve  food 
supplies  in  the  trunk.  In  the  case  of  the  maple  tree,  starch  and 
other  reserve  carbohydrates  are  in  process  of  transportation  to 
the  buds  in  the  form  of  sugars  which  may  be  recovered  as  such 
by  concentrating  the  sap. 

The  stems  of  some  plants  have  the  appearance  of  roots  fro: 
the  fact  that  they  exist  below  the  surface  of  the  soil.     The 
of  the  peanut,  for  example,  ripen  in  the  ground  because  the  flowe 
stems  lengthen  and  penetrate  the  soil  as  soon  as  the  blossom  falls. 

Root  stocks  or  rhizomes  are  subterranean  stems,  each  joint  or 
node  of  which  puts  out  both  leaf  buds  and  roots.     Each  node  is 
thus  equipped  to  become  an  independent  plant  as  soon  as  it 
isolated  from  the  parent  stem.     It  is  to  this  fact  that  the  e 
treme  troublesomeness  of  quack  grass  is  due.     Cultivation,  e 
cept  in  a  favorable  season  of  prolonged  drought,  serves  to  i 
crease  the  pest.     Asparagus  is  another  example  of  a  plant  gro 
ing  from  a  rhizome  and  well  illustrates  the  function  of  the  ste 
as  a  food  magazine. 

Tubers  are  fleshy  enlargements  of  the  tips  of  subterrane 
stems.     Their  ''eyes"  mark  the  position  of  buds,  which  disti 
guish  them  from  true  roots.     Each  of  these  eyes  is  the  precu 
of  one  or  more  new  plants.     The  tubers  of  the  potato,  arro 
root,  and  some  other  plants,  are  of  great  value  as  food  beca 


The  Plant.  85 

of  their  high  starch  content.  In  these  cases  the  stems  serve  as 
storage  places  for  reserves  of  plant  food.  The  bulbs  of  the  onion, 
lily  and  other  plants,  are  permanent  buds,  formed  of  fleshy, 
closely  packed  scales.  They  are  properly  a  part  of  the  stem  of 
the  plant,  serving  as  reserve  material  for  growth.  The  fleshy 
portion  of  the  crocus,  gladiolus  and  some  other  plants  is  not  a 
bulb,  but  is  an  enlargement  of  the  base  of  the  stem. 

The  stem  also  serves  as  a  means  of  support  for  the  leaves  and 
fruit,  favoring  the  exposure  of  both  to  the  air  and  sunlight,  es- 
sential to  the  chemical  processes  which  promote  growth. 

The  leaf.  The  leaf  is  the  seat  of  greatest  constructive  activity 
in  the  plant.  The  important  process  of  transpiration,  or  escape 
of  water  from  the  plant,  is  controlled  by  minute  openings  upon 
the  plant's  surface.  These  openings,  known  as  stomata,  occur 
in  small  numbers  upon  the  stems  of  plants,  but  they  are  most 
abundant  upon  the  leaves.  They  are  especially  numerous  upon 
the  protected  under  surface  of  leaves,  where,  as  in  the  case  of  the 
cabbage  or  apple,  their  number  may  reach  200,000  per  square 
inch.  The  outlet  of  a  stoma  is  lined  by  two  peculiar  cells  which 
face  each  other,  forming  a  miniature  mouth  opening  outward 
from  the  surface  of  the  leaf.  These  cells,  called  guard  cells,  are 
the  seat  of  control  in  the  action  of  the  stomata.  When  the  water 
supply  is  abundant  and  the  plant  cells  are  turgid,  the  guard  cells 
are  elongated  vertically  to  the  leaf  surface  and  contracted  par- 
allel to  it,  thus  drawing  apart  and  exposing  an  outlet  for  the 
evaporation  of  water.  On  the  other  hand,  when  the  water  sup- 
ply is  limited  and  the  plant  cells  wilt  or  shrink,  the  guard  cells 
flatten  and  become  elongated  parallel  to  the  leaf  surface,  thus 
automatically  closing  the  stomata  and  checking  evaporation  from 
the  plant.  This  process  partly  controls  the  supplying  of  plant 
food  from  the  soil  and  is  an  important  means  of  maintaining 
optimum  temperatures  in  the  plant  as  a  result  of  increased  or 
decreased  evaporation  of  water. 

The  leaf  inhales  air  through  the  stomata.  From  this  supply 
of  air  it  assimilates  carbon  dioxide  for  the  construction  of  plant 


86  Agricultural  Chemistry. 

compounds  and  employs  oxygen  in  the  process  of  respiration  ana- 
logous to  that  of  animals. 

The  magnitude  of  the  former  process  can  be  realized  when  we 
recall  that  a  12  ton  crop  of  corn  requires  for  its  production  four 
tons  of  carbon  dioxide.  To  secure  this  amount,  the  plants  must 
respire  10,000  tons  of  air  or  approximately  one-fourth  of  the 
total  amount  over  an  acre  of  land. 

The  construction  of  organic  compounds,  which  is  a  character- 
istic function  of  the  plant  occurs  principally  in  the  leaf.  It  is 
initiated  by  the  green  coloring  matter  known  as  chlorophyll. 
This  substance  has  been  shown  to  be  a  specific  but  complex  chem- 
ical compound.  It  may  be  seen  under  the  microscope  as  granules 
clustered  within  the  cells  of  all  green  plant  tissues.  In  some 
colorless  fungi  and  lower  plants  it  is  lacking.  Such  plants  do 
not  construct  organic  compounds  independently  but  derive  them 
from  previously  existing  vegetation.  The  green  color  of  plants 
is  due  to  chlorophyll,  as  may  be  shown  by  extracting  it  with 
alcohol.  Such  an  extract  is  intense  green  in  color,  due  to  the 
chlorophyll  removed  by  the  alcohol,  while  the  extracted  tissue  is 
bleached  and  colorless.  In  some  unexplained  manner  this  sen- 
sitive compound,  under  the  influence  of  light,  induces  the  union 
of  carbon  dioxide  assimilated  from  the  air,  and  water  conveyed 
from  the  root,  with  the  production  of  the  first  carbohydrates  of 
the  plant. 

It  is  not  known  whether  this  first  product  is  starch,  sugar,  or 
a  simple  precursor  of  these  compounds.  The  process  involves 
the  elimination  of  two  parts  of  oxygen  for  each  part  of  carbon 
dioxide  assimilated,  as  shown  by  the  following  general  expres- 
sion:— Carbon  dioxide  +  Water  =  Carbohydrate  (Dextrose) 
+  Oxygen. 

The  evolution  of  oxygen  in  this  process  has  been  proved  by  ex- 
periments in  which  living  leaves  were  confined  in  inverted  jars 
of  water.  A  gas  which  collected  above  the  water  responded  to 
tests  for  oxygen  and  its  volume  was  found  to  be  equivalent  to  the 
carbon  dioxide  taken  up.  The  plant  also  performs  through  the 


The  Plant.  87 

leaves  the  process  of  respiration  or  breathing,  in  which  oxygen 
of  the  inspired  air  combines  with  compounds  of  the  plant,  with 
an  accompanying  elimination  of  carbon  dioxide.  This  process 
is  most  evident  in  darkness  since  it  is  not  masked  then  by  the 
more  extensive  process  of  carbon  dioxide  assimilation.  By  com- 
bining the  carbohydrates  as  a  basal  material  with  nitrogen  and 
sulphur  brought  from  the  soil,  the  leaf  cells  produce  a  further 
class  of  organic  compounds  known  as  proteins.  Nitrogen  and 
sulphur  usually  enter  the  plant  as  highly  oxidized  compounds 
and  are  built  into  the  proteins  after  suffering  reduction  or  loss  of 
oxygen. 

The  leaf  functions  also  as  a  temporary  reservoir  for  migratory 
compounds  which,  at  the  death  of  this  organ,  return  into  the 
general  circulation  of  food  materials  in  the  plant.  This  is  true 
particularly  of  trees  and  other  perennial  plants,  whose  dead 
leaves  are  skeletons  consisting  chiefly  of  cellulose  compounds  and 
unessential  ash  constituents  like  silica,  the  more  important  nu- 
trient compounds  and  ash  materials  having  returned  to  the  stem 
of  the  plant. 

Flowers,  fruits,  and  seeds  are  pre-eminently  seats  of  construc- 
tive processes  in  which  chemical  reactions  are  especially  active 
and  significant.  Fragmentary  protein  structures,  possibly  the 
amino-acids,  are  here  withdrawn  from  solution  in  the  sap  cur- 
rent and  retained  as  finished  proteins.  Soluble  carbohydrates 
are  converted  to  starch  or  to  some  of  the  fats,  which  are  present 
in  the  seeds.  Ash  constituents  for  the  young  plant  of  the  next 
generation  are  stored  away  as  constituents  of  organic  compounds. 
Absorption  of  oxygen  is  especially  marked  in  these  organs  and 
may  be  accompanied  by  considerable  heat  production.  In  the 
ease  of  the  Italian  arum  lily  it  has  been  observed  that  the  large 
pistil  absorbs  in  one  hour  nearly  30  times  its  volume  of  oxygen 
with  a  resultant  temperature  of  over  100°  Fahr. 

The  end  of  all  this  activity  is  the  production  of  mature  seed 
containing  a  finished  plant  embryo,  a  store  of  food  materials,  and 
enzymes  to  inaugurate  the  process  of  germination.  At  this  stage 


88  Agricultural  Chemistry. 

of  growth,  the  leaves,  stems  and  roots  are  contributing  their  re- 
serves for  the  production  of  seed.  Migration  of  food  constituents, 
especially  of  starch,  nitrogen  compounds  and  ash  constituents, 
from  the  root  or  leaves  now  assumes  prominence.  While  the  ash 
constituents  accumulate  in  the  seed  only  in  small  amounts, 
sufficient  for  the  growth  of  a  vigorous  seedling,  some  of  the 
organic  reserve  compounds  may  be  stored  in  excess,  giving  dis- 
tinctive character  to  the  seed.  This  is  true  of  starch,  which  gives 
the  cereal  grains  peculiar  value  for  the  manufacture  of  foodstuffs 
and  of  alcoholic  products.  It  is  also  true  of  fats  and  proteins, 
which  give  to  cotton  and  flaxseed  high  commercial  values  as 
sources  of  oils  and  as  protein-furnishing  constituents  of  rations 
for  live  stock.  Starch  and  fat  serve  the  young  seedling  as 
sources  of  energy  for  growth  and  as  material  for  carbohydrate 
construction  until  it  becomes  independent  of  the  seed;  the  pro- 
teins of  the  seed  furnish  simple  nitrogenous  structures  from 
which  the  proteins  of  the  seedling  are  formed. 

Compounds  of  the  plant.  As  a  result  of  the  activity  of  the 
various  plant  organs,  there  is  produced  a  great  variety  of  com- 
pounds, partly  transitory  in  nature  and  partly  of  permanent 
character.  The  following  classification  is  a  brief  plan  of  division 
for  the  compounds  of  the  plant : 

("Carbohydrates 
Water  ^        Non-         I  Fats  and  waxes 

I  Nitrogenous  i  Terpenes  and  essential  oils 


Dry  Matter 


1i>  iirogeiiouM  i  ierpenes  aim 
I  Organic  acids 
f  Proteins 
XT:X J  Amino-acids 


VNitrogenoasj— -des 

lAmines  and  alkaloids 
Ash  containing   (  Salts  of  organic  acids 
compounds       (  Inorganic  compounds 


Water  holds  a  place  in  the  chemistry  of  the  plant  the  import- 
ance of  which  can  hardly  be  realized.  Besides  its  physical  func- 
tions of  transporting  food  materials  and  regulating  the  tempera- 
ture of  the  plant,  it  is  responsible  for  maintaining  the  turgidity 
of  the  individual  cells,  thus  giving  form  and  rigidity  to  immature 


The  Plant.  89 

and  succulent  growth.  The  entrance  of  many  comparatively  in- 
soluble compounds  into  the  plant  is  made  possible  when  they 
assume  a  hydrated  form,  that  is,  when  they  are  combined  with 
water.  Silicon,  for  example,  which  forms  comparatively  insol- 
uble soil  compounds,  is  supposed  to  enter  the  plant  as  silicic  acid, 
which  through  dehydration  or  loss  of  water  becomes  deposited 
as  silica.  Water  is  the  chief  constituent  in  green  plants,  its 
amount  varying  from  80  per  cent  in  grasses  to  90  per  cent  in 
root  crops.  Its  amount  decreases  at  the  maturing  stage.  For 
example,  timothy  grass,  which  contains  on  the  average  80  per 
cent  of  water,  has  when  dead  ripe  63  per  cent  of  this  constit- 
uent. 

The  importance  of  water  in  the  transformation  of  carbohy- 
drates will  be  shown  in  following  paragraphs.  It  is  important 
to  observe  here  that  the  constituents  of  water  form  55.5  per  cent 
of  starch  and  that  their  proportion  is  equally  prominent  in  other 
carbohydrates.  Water  bears  similar  importance  in  the  structure 
and  transformations  of  all  the  other  plant  compounds. 

The  carbohydrates  form  a  widely  distributed  and  prominent 
group  of  compounds  in  the  plant  kingdom.  They  may  be  classed 
in  order  of  increasing  complexity  as  follows: 

Mono-saccharides. 

Di-saccharides. 

Tri-saccharides. 

Poly-saccharides. 

Mono-saccharides  are  commonly  represented  by  dextrose  or 
glucose,  which  occurs  in  most  fruits.  Artificial  dextrose  or  "  glu- 
cose syrup ' '  is  prepared  commercially  by  the  action  of  hot,  dilute 
sulphuric  acid  upon  starch  and  subsequent  removal  of  the  acid 
by  means  of  lime.  This  is  a  hexose  or  six-carbon  sugar,  being 
composed  of  six  parts  of  carbon  combined  with  the  equivalent  of 
six  parts  of  water.  This  structure,  to  which  the  name  carbo- 
hydrate (signifying  carbon-water  union)  owes  its  origin,  may  be 
confirmed  by  gently  heating  the  sugar  in  a  glass  tube.  Water 
separates  from  the  compound  and  collects  on  the  adjacent  cold 


90  Agricultural  Chemistry. 

surface  of  the  tube,  while  the  remaining  blackened  or  charred 
portion  denotes  the  presence  of  carbon.  Glucose  is  a  product  of 
the  decomposition  of  all  higher  carbohydrates.  It  is  about  two- 
thirds  as  sweet  as  common  sugar. 

5L^  Levulose  or  fructose  is  a  mono-saccharide  of  the  samp  general 

Vv/Vcomposition  as  dextrose  and  has  many  properties  in  common  with 

it.     The  two  sugars  are  commonly  associated  in  fruits.     Levulose 

is  abundant  in  honey  where  it  exceeds  the  amount  of  dextrose. 

the  two  forming  about  75  per  cent  of  the  product. 

No  other  hexose-sugars  occur  free  in  plants,  but  galactose  is  n 
compound  of  this  class.  It  is  formed  by  hydrolysis  or  addition 
of  water  to  a  group  of  poly-saccharides,  called  galactans,  which 
occur  in  plants. 

Di-saccharides  are  represented  in  the  plant  kingdom  by  two 
sugars.  Sucrose,  or  cane  and  beet  sugar,  occurs  in  many  plants, 
notably  in  the  juice  of  sugar  cane  (16  to  18  per  cent),  in  the 
sugar  beet  (10  to  18  per  cent) ,  and  in  the  sap  of  the  sugar  maple 
(about  90  per  cent  of  the  solids).  The  sweetness  of  the  sap  of 
corn  and  sorghum  stalks  and  of  peas  and  other  seeds  is  due  to 
appreciable  amounts  of  sucrose.  This  sugar  differs  from  the 
mono-saccharides  in  that  it  crystallizes  readily,  and  this  property 
is  taken  advantage  of  in  purifying  the  commercial  product.  By 
the  action  of  the  enzyme  invert  in,  which  occurs  in  yeast,  sucrose 
is  converted  into  equal  parts  of  dextrose  and  levulose,  hence  the 
designation  ' '  di-saccharide. ' ' 

This  process  of  '  'Inversion  * '  may  be  accomplished  also  by  boil- 
ing sucrose  with  dilute  acids,  the  product  by  both  methods  being 
known  as  "invert  sugar. "  The  change  involves  the  addition  of 
one  part  of  water  to  each  part  of  cane  sugar  and  this  reaction 
characterizes  the  inter-relations  of  carbohydrates  in  general, 
which  are  largely  dependent  upon  differences  in  content  of  the 
water-forming  elements. 

Maltose  or  malt  sugar,  is  a  di-saccharide  occurring  in  small 
amounts  in  seeds.  Its  amount  is  considerably  increased  as  a 
result  of  germination,  in  which  the  enzyme  known  as  diastase 
converts  starch  to  dextrines  and  maltose.  Crystallized  maltose 


The  Plant.  91 

contains  one  part  of  water.  This  makes  possible  a  direct  con- 
version to  lower  sugars,  and  upon  inversion  by  enzymes  or  acids, 
one  part  of  this  sugar  yields  two  parts  of  dextrose. 

Tri-saccharides  are  represented  in  plants  by  raffinose.  This 
sugar  occurs  in  cotton  seed  and  the  germs  of  wheat,  barley  and 
other  seeds.  It  sometimes  occurs  in  sugar  beets,  especially  as  a 
result  of  disease  or  injury,  and  in  quantity  sufficient  to  interfere 
with  the  refining  of  the  beet  sugar.  Raffinose  inverts  to  equal 
parts  of  dextrose,  levulose  and  galactose. 

Poly-saccharides  are  the  most  abundant  of  the  carbohydrates. 
Starch,  which  is  one  of  the  simpler  members  of  this  group  of  com- 
pounds, is  an  unknown  multiple  of  a  chemical  group  containing 
six  parts  of  carbon  and  the  equivalent  of  five  parts  of  water.  It 
may  be  considered  as  a  multiple  of  the  compound  dextrose,  in 
which  each  part  of  dextrose  has  lost  one  part  of  water.  Diastase 
of  sprouting  seeds  and  the  enzyme  ptyalin,  which  occurs  in  saliva, 
convert  starch  to  a  mixture  of  simpler,  gummy  carbohydrates, 
known  as  dextrines  and  then  to  maltose. 

Hot,  dilute  acids  invert  starch  completely  to  dextrose  and  by 
this  means,  in  addition  to  the  action  of  diastase,  the  chemist  de- 
termines the  amount  of  starch  in  plants.  This  process  is  also, 
as  has  been  stated,  the  basis  for  the  commercial  production  of 
corn  syrup  or  glucose  syrup.  The  large  amounts  of  starch  in 
cereal  grains,  as  barley  and  corn,  and  in  some  root  crops,  as  the 
potato,  give  them  value  for  the  production  of  alcohol  and  alco- 
holic liquors.  Alcohol  is  not  formed  directly  from  starch,  but 
is  a  product  of  the  fermentation  of  the  sugars  to  which  starch 
may  be  converted  by  malt  extract.  * 

The  amounts  of  starch  found  in  some  plants  and  plant  products 
are  as  follows,  expressed  in  per  cent  of  the  air  dried  material : 


Percent 

Wheat  flour 66.55 

Corn  meal  7 1 . 00 

Corn  plant  (ears  glazed) 15.40 

Corn  stover 0 .95 

Oat  meal . .  56 . 23 


Per  cent 

Rice  grain 79.4 

Barley  grain 62.0 

Potato  tnber 75.5 

Bean  grain 42 . 7 

Pea  grain 40.5 


92 


Agricultural  Chemistry. 


Some  of  the  grains  and  roots  named  above  are  familiar  as 
sources  of  commercial  starch.  This  is  true  of  corn  and  the  potato. 
Tapioca  is  a  starch  preparation  from  the  root  of  the  cassava  plant 
and  sago  starch  is  taken  from  the  interior  of  the  trunk  of  the 


%h>       $ 

*    ft        S 

*$Vi     * 


&& 

*    ^»--»    ^ 


Starch  granules  from  various  sources. 

sago  palm.     A  single  tree  of  the  latter  variety  may  yield  500 
pounds  of  sago. 

Individual  starch  granules  are  readily  detected  in  plant  cells 
by  means  of  the  microscope  and  under  these  conditions,  the  char- 
acteristic markings  of  the  granules  of  different  plants  become  of 
value  in  identifying  the  source  of  the  sample. 


The  Plant.  93 

Dextrine  of  commerce  is  a  mixture  of  compounds  varying  in 
complexity.  Its  gummy  nature  gives  it  value  as  an  adhesive 
paste.  Stick-labels  and  postage  stamps  are  coated  with  dextrine. 
Mixtures  of  dextrines  occur  in  the  grains  of  cereal  plants  and 
their  amount  increases  at  germination  as  a  result  of  the  decom- 
position of  starch.  The  relative  proportions  of  chemical  elements 
in  starch  and  the  dextrines  are  the  same,  but  the  latter  are  ap- 
parently simpler  groups  of  a  basal  compound  (C6  H10  05)r 
ascending  in  complexity  toward  the  composition  of  starch.  Dex- 
trines are  precursors  of  the  simple  carbohydrate  maltose,  which 
occurs  in  germinated  grains. 

Galactans  are  complex  poly-saccharides  occurring  particularly 
in  the  seeds  of  leguminous  plants,  in  some  of  which  they  are  the 
chief  carbohydrates.  In  the  process  of  hydrolysis,  these  com- 
pounds combine  with  water  to  form  the  comparatively  simple 
hexose  known  as  ' t  galactose. " 

Cellulose,  the  basal  constituent  of  woody  fibre,  is  a  poly-sac- 
charide  of  great  importance  for  its  tenacity  and  rigidity,  which 
give  form  and  resistence  to  the  walls  of  mature  plant  cells.  It 
rarely  occurs  free  in  the  plant,  but  rather  as  a  constituent  of 
compound  celluloses,  such  as  the  incrusting,  lignified  celluloses 
or  ligno-celluloses  of  cell  walls.  Cotton  and  hemp  fibres  are 
single,  elongated  plant  cells,  whose  walls  are  composed  of  nearly 
pure  cellulose.  By  treating  these  fibres  successively  with  hot, 
dilute  acid,  with  hot,  dilute  alkali  and  finally  with  chlorine  gas, 
and  washing  out  the  products  formed,  the  purest  known  cellulose 
has  been  obtained.  It  is  evident  that  to  resist  such  treatment 
this  compound  must  be  extremely  stable.  It  can  be  brought  into 
solution,  however,  by  certain  reagents,  and  when  treated  with 
strong  sulphuric  acid,  followed  by  diluting  with  water  and  boil- 
ing, it  is  broken  down  and  partially  converted  to  dextrose. 

This  brief  discussion  of  the  properties  of  the  various  carbo- 
hydrates in  connection  with  their  common  products  of  decompo- 
sition, may  serve  to  indicate  a  common  basis  of  structure  for  this 
group  of  plant  compounds.  Thus,  by  the  union  of  two  mono- 


94  Agricultural  Chemistry. 

saccharides,  we  have  a  di-saccharide.  An  addition  of  another 
simple  sugar  produces  a  tri-saccharide.  Further  increments  re- 
sult in  dextrines  of  increasing  complexity  and  decreasing  solu- 
bility until  we  have  as  a  product,  starch.  This  is  a  substance 
insoluble  in  cold  water  and  decomposes  with  some  difficulty. 

By  some  internal  re-arrangement  of  the  chemical  elements  in- 
volved in  the  carbohydrate  molecule,  we  may  have  cellulose  pro- 
duced instead  of  starch.  This  is  an  extremely  resistant  and 
comparatively  permanent  compound  in  which  apparently  the 
stability  of  the  carbohydrates  has  reached  a  maximum.  These 
constructive  processes  take  place  only  in  the  plant.  We  can  fol- 
low them  in  the  chemical  laboratory  only  in  a  reversed  order, 
proceeding  from  the  complex  to  the  simple.  Our  knowledge  is 
therefore  concerned  with  the  general  relations  of  these  com- 
pounds, rather  than  with  the  actual  changes  by  which  they  are 
successively  produced  in  the  plant. 

The  pectin  substances  and  pentosans  should  be  classed  under 
the  general  head  of  carbohydrates. 

Pectins  are  insoluble  bodies  which  occur  in  the  flesh  of  most 
unripe  fruits.  Upon  boiling  with  water  they  yield  various  poor- 
ly defined  compounds  of  gelatinous  nature,  sometimes  referred 
to  as  pectoses  or  pectic  acids.  It  is  to  these  bodies  that  the  "  set- 
ting" of  fruit  jellies  is  due.  On  treatment  with  weak  acids  or 
alkalies,  they  yield  simple  sugars,  thereby  disclosing  their  carbo- 
hydrate nature.  Besides  dextrose,  they  yield  a  class  of  sugars 
containing  five  parts  of  carbon  and  hence  designated  as  pentoses. 
The  mucilaginous  substances  of  flaxseed,  quince  fruit  and  parts 
of  many  other  plants,  are  of  pectin  nature. 

Pentosans  are  present  in  considerable  amounts  in  certain 
gummy  exudations  of  plants,  such  as  cherry  gum,  which  oozes 
from  wounds  on  trees  of  the  prunus  genus,  and  gum  arabic  of 
tropical  Acacias,  a  genus  of  leguminous  plants.  The  pentosans 
of  gum  arabic  yield  on  hydrolysis  a  pentose  sugar  called  arab- 
inose.  Xylose  is  a  pentose  sugar  obtained  from  the  so-called 
wood  gums,  or  pentosans  which  are  abundant  in  straws  and  some 


The  Plant.  95 

grains.  The  pentosans  are  intimately  associated  with  the  cellu- 
lose of  plant  tissue.  They  differ  from  their  corresponding  sugars, 
the  pentoses,  by  the  equivalent  of  one  part  less  of  water.  Upon 
boiling  with  dilute  mineral  acids  each  of  these  compounds  takes 
on  one  part  of  water.  Araban  yields  arabinose  readily,  while 
xylan  yields  xylose  only  gradually  under  these  conditions.  This 
behaviour  demonstrates  the  carbohydrate  nature  of  the  bodies 
under  consideration.  The  following  percentages  of  pentosans 
have  been  found  in  some  plant  materials: — 

Hays 20  per  cent 

Gluten  feed 17        " 

Linseed  meal . .- 13        " 

Brewers'  grains 24        " ' 

Wheat  Bran 24 

From  60  to  90  per  cent  of  these  compounds  in  feeding  stuffs 
disappears  from  the  digestive  tract  of  herbivora.  This  may  be 
partly  due  to  bacterial  fermentation.  Since  pentosans,  when 
assimilated  by  the  animal,  appear  to  have  a  value  similar  to  that 
of  starch,  it  is  evident  that  in  some  cases  they  may  be  of  con- 
siderable importance  as  constituents  of  the  carbohydrate  material^/ 
of  feeding  stuffs. 

Fats  are  uniform  in  their  general  composition,  consisting  of 
one  part  of  glycerine  combined  with  three  parts  of  fatty  acid. 
The  latter  constituent  controls  the  nomenclature  of  the  fats. 
Thus,  for  example,  the  fat  containing  three  parts  of  stearic  acid 
is  known  as  ' ' tri-stearin, "  or  more  commonly  as  "stearin."  Fats 
which  contain  two  or  three  different  fatty  acids  in  combination 
with  the  same  part  of  glycerine  are  called  "mixed  glycerides." 
Acetic  acid,  which  causes  the  sour  taste  in  vinegar,  is  a  typical 
example  of  the  fatty  acids,  the  simpler  members  of  this  group 
of  compounds  being  volatile  liquids  of  characteristic,  pungent 
odor  similar  to  that  of  the  acid  cited.  The  higher  members  of 
the  acetic  acid  series  are  solid  substances ;  and  the  fats  in  which 
they  occur  are  also  solid,  in  distinction  from  liquid  fats  or  oils 


96  Agricultural  Chemistry. 

produced  by  lower  fatty  acids.  These  acids  rarely  occur  free,  as 
in  the  case  of  formic  acid,  which  produces  the  sting  of  the  nettle 
plant;  but  they  usually  occur  as  constituents  of  neutral  fats. 
Oleic,  linoleic  and  linolenic  acids  are  types  of  three  other  series 
of  fatty  acids  which  are  more  abundant  in  plants  than  the  acetic 
acid  series.  In  distinction  from  the  latter,  these  acids  are  char- 
acterized by  loose  chemical  bonds,  by  virtue  of  which  their  fats 
take  on  oxygen,  iodine  and  other  active  chemical  elements. 
Thus,  on  prolonged  exposure  to  air,  olein  takes  up  one  part  of; 
oxygen,  linolein  takes  up  two  parts  and  linolenin  takes  up  three 
parts,  by  weight.  This  change  is  accompanied  in  proportion  to 
its  extent  by  ' '  setting ' '  or  hardening  of  the  oils  concerned.  As 
a  result,  while  olein  remains  liquid  even  when  exposed  to  the  air 
in  thin  layers  and  is  characterized  as  a  "non-drying"  oil,  in- 
creasing proportions  of  linolein  and  linolenin  produce  con- 
secutively the  "semi-drying"  and  "drying"  oils. 

The  high  percentages  of  the  latter  oils  in  linseed  oil  enhance 
its  value  as  a  vehicle  for  paints,  because,  having  distributed  the 
pigments  which  it  carries,  it  gradually  "sets"  and  forms  a  du- 
rable protective  coating.  If  the  process  of  oxidation  in  such  an 
oil  is  hastened  by  exposing  it  in  thin  layers  upon  inflammable 
material,  sufficient  heat  may  be  generated  to  cause  spontaneous 
combustion.  Ignorance  of  this  fact  has  caused  destructive  fires, 
due  to  oil  soaked  rags  and  similar  material. 

Plant  fats  consist  for  the  most  part  of  mixtures  of  olein  and 
linolein  with  smaller  amounts  of  stearin,  palmitin  and  lower: 
members  of  the  acetic  acid  series.  The  proportions  of  fats  ar« 
such  as  to  maintain  a  liquid  state  at  ordinary  temperatures  and" 
produce  the  oils  of  the  seed  of  cotton,  castor  bean,  flax  and  other 
plants.  The  simple  fats  differ  from  carbohydrates  by  a  higher 
content  of  carbon  and  hydrogen  and  lower  oxygen  content  than 
the  latter.  This  higher  content  of  combustible  elements  renders 
fats  of  greater  fuel  value  than  the  other  leading  plant  compounds, 
because  of  greater  oxygen  consumption  during  combustion.  This 


The  Plant.  97 

property  assumes  great  importance,  as  a  source  of  heat  or  energy, 
when  the  fats  are  oxidized  in  the  sprouting  seed  or  in  the  animal 
body. 

In  some  remarkable  manner,  the  plant  reverses  this  process  and 
constructs  its  fats  from  carbohydrates  with  elimination  of  oxy- 
gen. The  following  figures  show  the  relative  composition  of  a 
typical  carbohydrate  and  a  typical  fat. 

Per  cent          Per  cent          Per  cent 
Carbon          Hydrogen         Oxygen 

Carbohydrate  (starch) 39-98  6.71  53.31 

Fat  (stearin) 76.78  12.45  10.77 

Fats  occur  in  plants  chiefly  as  reserves  in  the  seed.  The  seeds 
of  cereal  plants  such  as  corn  and  oats  contain  only  small  amounts 
of  fat.  Flaxseed,  cotton-seed,  the  castor  bean  and  other  seeds 
contain  oil  in  sufficient  amount  to  render  its  extraction  on  a  com- 
mercial scale  both  feasible  and  profitable.  The  fat  content  of 
i'cme  common  seeds  is  as  follows: — 


Per  cent 

Barley  1.8 

Whefct 20 

Con. 5.0 

Oats  .  5.0 


Per  cent 

Cotton 20.0 

Sunflower 21.0 

Flax 33.5 

Castor  bean..  50.0 


The  old  fashioned  home  process  of  soap-making  by  boiling 
waste  grease  with  leachings  from  wood  ashes  depends  upon  the 
fact  that  alkali  metals,  in  this  case  the  potassium  or  '  *  potash ' '  of 
wood  ashes,  will  displace  glycerine  from  fats.  Super-heated 
steam  also  breaks  up  fats  into  glycerine  and  fatty  acids,  and  in 
common  with  the  alkali  treatment  mentioned  above,  the  process 
is  called  saponification.  The  glycerine  of  commerce  is  a  by- 
product from  this  process  in  the  soap  industry.  Since  mineral 
oils  cannot  be  saponified,  we  have  here  a  means  of  distinguishing 
them  from  fats. 

Lecithin  is  a  compound  closely  related  to  the  fats.  In  place 
of  one  part  of  fatty  acid  in  a  normal  fat  it  contains  phosphoric 
acid  combined  with  a  nitrogen-containing,  basic  compound  known 


98'  Agricultural  Chemistry. 

as  choline.  Lecithin  is  sometimes  referred  to  as  a  "  phosphorized 
fat."  It  occurs  in  the  seeds  of  cereals  and  to  a  gr3ater  extent 
in  the  seeds  of  legumes. 

Waxes  have  some  properties  in  common  with  the  fats  and  are 
frequently  associated  with  them  in  the  plant  and  separated  with 
them  by  methods  of  extraction.  They  differ  from  fats  in  that 
they  contain  an  alcohol  of  higher  weight  in  place  of  glycerine, 
this  alcohol  being  combined  with  the  fatty  acid  in  equal  parts. 
Chinese  wax  and  the  carnauba  wax  obtained  from  the  leaves  of 
a  South  American  palm  are  single  compounds,  while  the  waxes 
found  in  the  seeds  of  the  palm,  flax,  cotton  and  other  plants  are 
mixtures.  The  "bloom"  of  leaves  and  fruits,  which  serves  as 
a  protective  coating,  is  composed  of  waxes.  These  compounds 
can  be  converted  to  soaps  in  the  same  manner  as  fats,  but  they 
yield,  of  course,  other  alcohols  in  place  of  glycerine. 

Terpenes,  essential  oils,  camphors  and  resins  form  another 
group  of  closely  related  plant  compounds.  The  terpenes  belong 
to  a  class  of  chemical  compounds  known  as  hydro-carbons,  which 
are  composed  of  the  elements  carbon  and  hydrogen  only.  They 
are  partly  liquids,  such  as  spirits  of  turpentine,  and  partly  solids, 
such  as  rubber  and  gutta-percha.  As  in  the  case  of  carbohy- 
drates, a  classification  of  these  bodies  in  order  of  complexity  is 
in  use  which  separates  them  into  mono-,  di-  and  poly-terpenes. 
Terpenes  are  products  of  pitch  yielding  trees.  Turpentine  is  a 
terpene  of  special  value  in  the  paint  industry  as  a  "thinner" 
or  solvent  for  fats  and  oils. 

The  essential  oils  to  which  the  characteristic  odors  of  flowers 
and  flavors  of  fruits  are  due  are  partly  hydro-carbons,  as  in  the 
case  of  oil  of  turpentine  and  oil  of  lavender.  Others,  such  as  oil 
of  wintergreen  and  almond  oil,  contain  some  oxygen.  Heliotro- 
pin  of  the  heliotrope  and  the  compounds  to  which  the  aroma  of 
the  banana,  orange  and  other  fruits  is  due,  are  essential  oils.  The 
pleasing  smell  of  new  mown  hay  is  due  to  the  essential  oil,  cou- 
marin.  These  compounds  are  of  value  in  the  compounding  of 
perfumes,  cordials  and  medicines.  They  are  of  special  signific- 
ance in  foods  because  of  their  probable  effect  on  palatability. 


The  Plan  I.  99 

Camphors  are  obtained  by  the  distillation  of  certain  tropical 
woods.  They  differ  from  terpenes  in  containing  oxygen  added 
to  the  elements  of  the  latter.  The  two  classes  of  compounds  are 
apparently  closely  related  products  of  the  chemical  processes  of 
the  plant. 

Eesins  occur  in  pitches  and  are  closely  allied  in  composition  to 
the  camphors.  Like  terpenes  and  camphors  they  may  be  distin- 
guished from  fats  by  failure  to  produce  soaps  by  the  usual 
process  of  saponification. 

Organic  acids  often  occur  in  plants  in  considerable  amounts 
and  are  responsible  for  the  sour  taste  frequently  observed.  They 
are  produced  by  the  fermentation  of  carbohydrates  and  rarely 
occur  free  but  usually  as  acid  or  neutral  salts  of  potassium  or 
calcium.  The  sourness  of  lemons  is  due  to  critic  acid.  The  acid- 
potassium  salt  of  oxalic  acid  occurs  in  sorrel  and  acid-calcium 
oxalate  has  been  found  in  rhubarb.  Malic  acid  is  common  in 
1'ruits,  and  exists  as  the  acid-potassium  salt  in  rhubarb  and  the 
acid-calcium  salt  in  the  berries  of  the  mountain  ash,  tobacco 
leaves  and  other  plants.  The  acid-potassium  salt  of  tartaric 
acid  is  characteristic  of  the  grape,  and  potassium  and  calcium 
salts  of  this  acid  are  found  in  the  pine-apple,  sumac  berry  and 
other  fruits.  It  is  interesting  to  note  in  this  connection  that 
lactic  acid  develops  in  corn  silage  as  a  product  of  hydrolysis  of 
dextrose  and  other  carbohydrates.  These  acid  compounds  play 
an  important  part  in  the  production  of  characteristic  flavors. 

The  proteins  are  compounds  of  the  greatest  importance  in  the 
plant.  They  are  of  complex  structure,  containing  not  only  car- 
bon, hydrogen  and  oxygen,  but  also  nitrogen  and  sulphur.  This 
large  number  of  constituents  makes  possible  a  variety  and  com- 
plexity of  structure  fitting  them  for  the  delicate  and  complicated 
reactions  which  characterize  life  processes.  Proteins  form  the 
basis  of  the  life-bearing  protoplasm  and  nucleus  of  each  plant 
cell.  Although  contained  in  every  cell,  they  are  localized  chiefly 
in  the  seed  and  furnish  nitrogen  for  the  first  protein  structures 
of  the  seedling.  Individual  proteins  are  characterized  by  a  con- 


100  Agricultural  Chemistry. 

tent  in  fixed  proportion  of  the  simpler  nitrogenous  bodies  known 
as  amino-acids.  Asparagin,  which  is  a  derivative  of  an  amino- 
aeid,  occurs  in  freshly  sprouted  asparagus,  peas  and  beans.  It 
is  produced  from  seed  proteins  by  enzyme  action  and  is,  in  part, 
eventually  fitted  into  the  proteins  of  the  seedling. 
Plant  proteins  may  be  classified  briefly  as  follows : 

1.  Albumins:     Soluble   in  pure  cold  water;   coagulated  by 
boiling ;  occur  in  seeds  only  in  small  amounts. 

2.  Globulins:     Insoluble  in  water;  soluble  in  salt  solutions; 
separate  out  on  diluting  or  saturating  the  solution.     Most  com- 
mon and  abundant  of  plant  proteins.     Occur  in  largest  amount 
in  the  seeds  of  leguminous  plants.     Certain  globulins  appear  to 
be  characteristic  of  the  seed  in  which  they  are  found,  as  with 
avenalin  of  the  oat,  maysine  of  corn,  and  hordein  of  barley. 
Edestin,  the  globulin  of  the  hemp  seed,  however,  occurs  in  sev- 
eral grains. 

3.  Alcohol' soluble  proteins:    (Prolamins).    Nearly  or  wholly 
insoluble  in  water;  soluble  in  alcohol  of  from  70  to  90  per  cent 
strength.     They  have  been  found  only  in  the  seeds  of  cereal 
plants. 

4.  Glutelins:     Not  dissolved  by  water,  salt  solutions,  or  al- 
cohol; may  be  extracted  by  treating  the  residue  of  seeds  from 
which  the  other  proteins  have  been  removed,  with  dilute  alkaline 
solutions.     Isolated  and  purified  with  much  difficulty.     The  only 
well  defined  glutelins  are  glutenin  of  the  seed  of  wheat  and  orys- 
enin  of  the  seed  of  the  rice. 

5.  Conjugated   (compound)  proteins:     These  proteins  have 
been  modified  by  combining  with  other  compounds.     They  in- 
clude nucleo-proteins,  in  which  a  large  proportion  of  protein  is 
combined  with  a  small  amount  of  nucleic  acid.     Phosphorus  is 
present  in  these  compounds,  being  contributed  by  the  nucleic 
acid.     Conjugated  proteins  of  other  types  occur  in  the  animal 
kingdom,  but  the  exact  nature  of  other  preparations  than  nucleo- 
proteins  from  plants,  assigned  to  this  group  of  compounds,  has 
not  been  clearly  established.     Such  knowledge  as  we  possess  in- 


The  Plant. 


101 


dicates  that  only  small  quantities  of  nucleo-proteins  occur  in  the 
entire  seed  and  that  they  are  chiefly  in  the  tissues  of  the  embryo, 
in  which  the  nuclei  of  cells  are  most  abundant. 

The  approximate  amounts  of  some  plant  proteins  found  in 
seeds  are  given  by  Osborne  as  follows : 


Protein 


Source 


Per  cent  in  the 
dry  material 


Albumins 
Leucosin 

1 
Wheat  grain         '      n  a  -n  A. 

Leucosin 

Rye  grain  .       

0.43 
0.3 
2.0 

2.0 
1.25 

1.5 
1.5 

0.25 
20.00 
1.5 
26.2 
10.0 

10.0 
13.0 

17.0 
0.14 
0.6  -0.7 
15.83 
17.6 

4.00 
4.25 
4.00 
5.00 

4.0  -4.5 
:>  5  (assumed) 
11.25 

4.50 

Leucosin 

Bar'ev  grain  

Phaselin 

Kidney  bean  grain  

Legumelin 

Pea  meal  (free  from  outer 
seed  coats)  .     .  .         ... 

L6°rumelin 

Lentil   meal    (free    from 
outer  seed  coats  ) 

Le°ruineli  n  

Horse    bean    meal    (free 
from  outer  seed  coats)  .  .  . 
Vetch  grain              

Legtiinelin   

Globulins 
May  sin 

Corn  train 

Phaseolin 

Kidney  bean  grain  
Oat  grain  

Avenalin  

Congrlutm  

Yellow  lupine  grain  
Vetch  grain 

Legumin 

Legumin  and  Vicilin  
Legumin  and  Vicilin  
•  Legumin  and  Vicilin  
Edestin  

Pea  meal  (free  from  outer 
coatin  s) 

Lentil    meal    (free  from 
outer  coatings)  
Horse    bean    meal    (free 
from   outer    coatings)... 
Corn   grain 

Edestin  

\Vheat  grain 

Edestin  
Edestin  

Cotton  seed  meal  (oil  free) 
Flax  ^eed  (^rain) 

Alcohol  soluble  proteins 
<  rliadin  .  . 

live  grain 

Gliadin 

"Wheat  grain 

'    Hordein  ,  

Barley  grain             

Xein  

Corn   grain  
Wheat  grain 

r            , 

Crlutelins 
Glurenin  
Glutenin  

Corn   grain 

(irlutf  llill 

Oat.  crrair* 

Glutenin                                   '*iirl°v  prain    ""  ""  •> 

102  Agricultural  Chemistry. 

Amino-acids,  which  have  been  referred  to  as  constituents  of 
proteins,  occur  free  to  a  limited  extent  in  plants.  Their  struc- 
ture is  that  of  fatty  acids  into  which  amino  (NH2)  groups  have 
been  substituted  for  hydrogen  atoms  other  than  those  of  acid 
radicles.  They  are  compounds  of  only  weakly  acid  or  even  of 
basic  properties.  Amino-valerianic  acid  is  a  body  of  this  sort 
which  has  been  separated  from  white  and  yellow  lupine  plants 
of  two  to  three  weeks'  age.  Leucin,  which  is  a  substituted  amino- 
acetic-acid,  occurs  in  smaller  amounts  with  the  amino-valerianic 
acid.  In  some  coniferous  seeds  the  amount  of  arginin,  another 
amino  acid,  exceeds  that  of  the  amino  acids  already  mentioned. 
Arginin  is  a  di-amino  acid,  that  is,  it  contains  two  such  amino 
groups. 

Amides  are  nitrogenous  compounds  of  another  class  which 
have  been  the  object  of  considerable  study  in  their  relation  to 
the  feeding  of  animals.  The  proportion  of  the  total  nitrogen  in 
this  form  at  the  time  of  harvesting  the  plant  is  of  considerable 
importance  because  of  the  probable  difference  in  feeding  value 
of  various  nitrogenous  compounds.  Amides  have  the  structure 
of  organic  acids,  into  which  amino  groups  have  been  substituted 
for  the  hydroxyl  group  of  acid  radicles.  They  are,  as  we  might 
therefore  expect,  neutral,  salt-like  bodies.  They  require  only  the 
addition  of  one  part  of  water  to  the  molecule  to  become  ammo- 
nium salts,  and  may  be  considered  as  derivatives  of  ammonia  as 
well  as  of  acids.  Asparagin  is  an  amide  found  in  many  plants, 
as  in  asparagus,  peas  and  beans,  especially  just  after  sprouting. 
Glutamin,  which  has  been  found  in  squash  'seedlings  and  beet 
juice  with  asparagin,  is  also  an  amide.  These  are  properly 
double  amino  compounds,  being  amides  of  amino-acids.  They 
offer  examples  of  the  possible  complexity  of  structure  of  organic 
nitrogenuous  compounds  even  in  their  simpler  forms.  The  ami- 
des and  amino-acids  which  occur  at  intermediate  stages  of  the 
growth  of  plants,  are  derived  from  the  disintegration  of  the  seed 
proteins,  or  from  constructive  processes  in  the  leaves  and  are  to 


The  Plant.  103 

a  greater  or  less  extent  precursors  of  protein  compounds  in  the 
new  seed.  Being  readily  soluble  in  water,  they  form  ready 
means  for  the  transportation  in  the  sap  of  protein  forming  struc- 
tures, and  can  be  placed  at  the  disposal  of  the  reconstructive 
forces  in  the  plant. 

Amines,  or  compound  ammonias,  have  only  a  limited  practical 
importance  as  plant  compounds.  They  are  strongly  basic  com- 
pounds resulting  from  the  replacement  of  hydrogen  in  ammonia 
by  hydrocarbon  radicles.  The  rank  odor  of  some  plants  as  the 
fetid  goose  foot  and  hawthorn  is  due  to  compounds  of  this  sort. 

Alkaloids  are  basic  organic  compounds  involving  substitution 
of  more  complex  organic  radicles  into  the  ammonia  molecule  than 
is  the  case  with  the  amines.  By  virtue  of  their  basic  structure 
they  combine  with  acids ;  the  salts  so  formed  offer  means  of  iso- 
lating and  purifying  these  bodies.  Some  of  the  more  common 
alkaloids  are  nicotine  of  tobacco ;  morphine  of  the  poppy ;  strych- 
nine, brucine  and  curarine  of  strychnos  wood ;  quinine  of  cinch- 
ona bark;  piperin  of  pepper;  solanin  of  the  potato  and  night- 
shade; and  cocaine  of  the  leaves  of  the  South  American  cocoa 
tree.  Some  are  of  medicinal  value  as  stimulants  (strychnine), 
others  act  as  narcotics  (nicotine,  morphine),  and  still  others  are 
virulent  poisons  (curarine,  solanin).  Curarine  is  the  active  con- 
stituent of  curare  extract  with  which  some  wild  tribes  poison 
their  arrow-tips. 

The  ash  constituents  of  the  plant,  usually  relatively  small  in 
amount,  are  for  the  most  part  absolutely  essential  to  its  life 
activities.  The  following  chemical  elements  are  always  found  in 
plant  ash:  Calcium,  potassium,  magnesium,  sodium,  iron,  phos- 
phorus, sulphur,  chlorine  and  silicon.  Manganese  and  aluminum 
are  occasionally  present ;  and  zinc,  barium  and  other  metals  some- 
times occur  as  accidental  constituents. 

The  following  brief  table  gives  the  amount  and  composition  of 
the  ash  of  some  typical  plants.  The  subject  will  be  taken  up 
more  in  detail  in  connection  with  the  relative  composition  and 
food  demands  of  crops. 


10-t 


Agricultural  Chemistry. 


Composition  of  the  Ash  of  Plants. 


Pure 

Ash  Constituents.     Per  cent  in  the  pure  ash. 

Ash 

per 

Plant 

cent 

"PK/M3 

Sul- 

in 
dry 

Pot- 
ash 

Soda 

Lime 

Mag- 
nesia 

Iron 
Oxide 

riios- 
phoric 

A  ,.\r\ 

phur 
tri- 

Silica 

Chlor- 
ine 

plant 

1 

A.C1Q 

oxide 

Timothy 

(hay)  

6.82 

34.69 

1.83 

8.05 

3.24 

0.83 

11.80 

2.85 

32.17 

5.19 

Clover  (early 

bloom)  

6.86 

32.29 

1.97 

34.91 

10.90 

1.08 

9.64 

3.23 

2.69 

3.78 

Wheat 

(grain)  .... 

1.96 

31.16 

2.07 

3.25 

12.06 

1.28 

47.22 

0.39 

1.96 

0.32 

Wheat 

(straw)  .  .  . 

5.37 

13.65 

1.38 

5.76 

2.48 

0.61 

4.81 

2.45 

67.50 

1.68 

Oat  (grain).  . 

3.12 

17-90 

1.66 

3.60 

7.13 

1.18 

25.64 

1.78 

39.18 

0.94 

Oat  (straw).. 

7.17 

26.42 

3.29 

6.97 

3.66 

1.16 

4.59 

&.21 

46.69 

4.37 

Potato 

(tuber)  

3.79 

60.06 

2.96 

2.64 

4.93 

1.10 

16.86 

6.52 

2.04 

3.46 

Sugar  beet 

(root)  

3.83 

53.13 

8.92 

6.08 

7.86 

1.14 

12.18 

4.20 

2.28 

4.81 

Corn  (grain). 

1.45 

29.7* 

1.10 

2.17 

15  52 

0.76 

45.61 

0.78 

2.09 

0.91 

Corn  (stalks) 

5.33 

36.30 

1  20 

10.80 

5.70 

2.30 

8.30 

5.30 

28.80 

1.40 

The  ash  constituents  of  plants  occurring  in  the  seed  are  present 
there  almost  entirly  as  constituents  of  organic  compounds.  The 
hulls  of  the  oat  and  other  grains,  which  are  not  a  part  of  the 
seed  proper,  have  been  found  to  contain  considerable  amounts  of 
inorganic  compounds,  among  which  silica  is  especially  notable. 
The  large  amount  of  this  ingredient  in  cereal  straws  is  supposed 
to  be  in  inorganic  form,  and  phosphorus  and  sulphur  have  been 
shown  to  be  present  in  the  stems  of  legumes  and  other  plants  at 
early  stages  of  growth  to  a  large  extent  as  constituents  of  inor- 
ganic compounds.  When  the  plant  is  burned,  sulphur,  phos- 
phorus and  other  acid  forming  elements  which  are  present  in 
organic  compounds,  are  converted  to  acid  radicles.  These  acid 
radicles  combine  with  basic  radicles  simultaneously  formed  from 
calcium,  potassium  and  other  metallic  elements  in  the  plant. 
This  results  in  the  production  of  inorganic  salts,  such  as  potas- 


The  Plant. 


105 


sium  sulphate  and  calcium  phosphate,  in  the  ash.  Any  excess  of 
the  basic  elements  over  the  acid  forming  elements  will  combine 
with  the  carbonic  acid  present  in  the  air  as  a  result  of  the  process 
of  combustion,  and  will  occur  in  the  ash  as  carbonates.  The  large 
amount  of  potassium  carbonate  in  wood  ashes  is  formed  in  this 
manner.  On  the  other  hand,  any  excess  of  acid  forming  elements 
in  the  plant  will  be  lost  by  volatilization  and  will  fail  to  appear 
in  the  ash.  It  is  thus  evident  that  the  composition  of  the  ash 
gives  little  clue  to  the  previous  status  of  its  constituents  in  the 
plant. 

In  some  cases,  as  with  corn  grain,  where  the  basic  elements  of 
the  plant  are  low,  a  large  part  of  the  sulphur  and  chlorine  may 
be  lost  during  incineration.  The  following  data  from  Fraps  il- 
lustrates this  point. 

Loss  of  Plant  Elements  by  Burning. 


Sulphur 

• 
Chlorine 

Total 
per  cent 

Per  cent 
determined 
from  ash 

Total 
per  cent 

Per  cent 
determined 
from  ash 

Corn  (seed) 

0.135 
0.186 
0.19(> 
0.44 
0.20 
0.188 

Trace 
0  03 
0.02 
0.07 
0.17 
0.05 

0.04 
0.008 
0.097 
0.032 

Trace 
0  005 

0.005 
0.008 

O.SK4 

Peas  (pe^d)  

Oats   (seed)  
Cotton  seed  (meal)  • 

iPeaiiiits  (fruit) 

0.888 

Timothy  (hay)  

In  timothy  hay  and  the  tobacco  leaf,  where  these  losses  have 
been  slight,  the  plants  contain  a  high  proportion  of  base  forming 
elements.  In  the  other  plants  tabulated  above,  a  lack  of  basic- 
constituents,  together  with  a  high  percentage  of  phosphorus,  pre- 
vents complete  retention  of  the  other  acid  forming  elements  dur- 
ing combustion.  With  corn,  Fraps  recovered,  as  an  ash  con* 
stituent.  but  one-fiftieth  of  the  total  sulphur  in  that  grain. 


106  Agricultural  Chemistry. 

Considerable  knowledge  has  accumulated  as  to  the  status  of 
these  ash  constituents  in  the  plant.  Their  functions,  however, 
are  in  many  cases  not  clearly  understood. 

Calcium  has  already  been  referred  to  as  a  constituent  of  salts 
of  organic  acids.  It  occurs  widely  distributed  in  this  form.  Al- 
though essential  to  the  plant  and  apparently  playing  an  impor- 
tant part  in  the  chemical  changes  of  living  cells,  its  specific  func- 
tion is  unknown.  In  some  cases  it  appears  to  be  of  advantage  in 
forming  insoluble  salts  of  organic  acids,  such  as  calcium  oxalate. 
thus  preventing  harmful  accumulations  of  free  acids  in  the  plant 
Loew  is  of  the  opinion  that  calcium-protein  compounds  exist  in 
the  organized  parts  of  plant  cells,  from  which  the  nucleus  and 
the  chlorophyll  bodies  are  built  up.  He  attributes  the  charac- 
teristic poisonous  action  of  soluble  oxalates  to  their  power  of  de- 
priving these  compounds  of  their  calcium,  converting  it  into  the 
insoluble  oxalate.  According  to  this  view,  calcium  is  partic- 
ularly essential  to  the  metabolic  processes  in  plants. 

Magnesium  exceeds  calcium  in  the  amount  present  in  seeds 
and,  according  to  Loew,  it  is  attended  by  phosphorus  and  favors 
the  assimilation  of  the  latter  body  by  retaining  it  in  the  form  of 
soluble  compounds.  In  the  same  manner,  its  abundant  supply 
in  the  seed  favors  easy  assimilation  of  the  reserve  phosphorus  of 
this  organ  by  the  seedling. 

Potassium  is  of  common  occurrence  as  a  constituent  of  the  salts 
of  organic  acids.  It  has  also  been  known  for  a  long  time  that" 
potassium  is  intimately  connected  with  the  formation  of  starch 
and  sugar  by  plants.  It  is  uniformly  abundant  in  the  ash  of 
plants  rich  in  these  carbohydrates.  The  lodging  of  cereal  grain 
plants  has  been  attributed  to  lack  of  potassium.  This  theory  is 
probably  based  upon  the  known  stimulating  effect  of  potassium 
on  the  formation  of  cellulose  and  the  simpler  carbohydrates  in 
plant  growth,  since  it  has  been  shown  that  lodging  is  due  in  some 
cases  to  lack  of  cellulose  compounds  in  the  cell  walls  of  the  plant. 
Stoklasa  has  recently  shown  that  potassium  is  a  constituent  of  the 
chlorophyll  of  grasses.  This  investigator  states  that  it  is  more 


The  Plant.  107 

abundant  in  the  chlorophyll  structures  than  in  other  parts  of 
the  plant.  Loew  calls  attention  to  the  efficiency  of  potassium  and 
its  compounds  in  condensing  certain  aldehydes.  He  attributes 
to  this  element  the  function  of  condensation  in  the  formation  of 
carbohydrates  and  proteins. 

Phosphorus  is  an  essential  constituent  of  the  nucleins  and  nu- 
cleo-proteins  around  which  the  activities  of  the  living  plant  cell 
are  centered.  This  element  is  also  a  constituent  of  the  active 
chlorophyll.  It  is  thus  seen  to  be  an  element  with  complex  and 
|  most  important  functions.  Phosphorous  is  also  a  constituent  of" 
lecithin,  the  chief  function  of  which  has  been  suggested  to  be  that 
of  receiving  fatty  acids  into  its  molecule  and  passing  them  on  in 
soluble  form  to  the  protoplasm  of  the  seedling.  It  would  thus 
serve  as  a  carrier  of  fats,  which  furnish  energy  for.  the  first 
growth  of  the  plant. 

Sodium  has  been  shown  to  be  dispensable  with  many  kinds  of 
plants.  There  is  some  evidence  that  sodium  chloride  or  common 
salt  favors  the  action  of  diastase  and  sodium  may  function  in 
this  way  in  the  transformations  of  carbohydrates.  A  consider- 
able amount  of  work,  especially  an  extended  series  of  plot  ex- 
periments at  the  Rhode  Island  Experiment  Station  with  various 
crops,  has  afforded  evidence  that  sodium  favors  economical  utiliz- 
ation of  a  low  potassium  supply,  particularly  when  relatively 
more  sodium  enters  the  plant. 

Sulphur  is  a  constituent  of  all  proteins.  It  forms  from  0.4  to 
4.0  per  cent  of  these  compounds.  It  is  a  constituent  of  other  or- 
ganic compounds  known  as  iso-sulpho-cyanates  or  mustard  oils, 
common  to  the  mustard,  turnip  and  other  cruciferous  plants. 
The  function  of  these  compounds  is  not  known. 

Iron  is  essential  to  green  plants  and  lack  of  it  produces  a  con- 
dition of  chlorosis,  in  which  the  leaves  become  bleached.  While 
chlorophyll  does  not  contain  iron,  its  action  is  absolutely  depend- 
ent upon  this  element,  small  amounts  of  the  latter  being  extremely 
effective.  Iron  is  a  constituent  of  organic  compounds  in  the 
nuclei  of  plant  cells. 


108  Agricultural  Chemistry. 

Chlorine  is  found  to  a  considerable  extent  in  the  asli  of  the 
mangel  and  other  root  crops.  It  exerts  beneficial  action  in  some 
cases  when  applied  as  a  fertilizer  in  the  form  of  the  sodium  salt. 
Nobbe  found  that  buck- wheat  failed  to  develop  beyond  the  flower- 
ing stage  when  lacking  a  supply  of  chlorine,  and  that  great  ac- 
cumulations of  starch  formed  in  parts  of  the  stems  of  the  plant 
under  investigation.  This  has  led  to  the  view  that  chlorine,  in 
the  form  of  the  sodium  salt,  is  essential  to  the  proper  activity  of 
diastase. 

Silicon  is  abundant  in  many  plants,  such  as  the  graminac 
(grass  family,  which  includes  the  cereal  grains),  equisetaceae 
(horse  tails)  and  the  ironwood,  cauto  and  other  trees.  "Wicko 
found  that  the  ash  of  the  cauto  tree  contained  96  per  cent  of  sil- 
ica: and  the  ash  of  the  common  scouring  rush  (Equisetuni  hye- 
male)  has  been  found  to  contain  97.5  per  cent  of  this  constituent. 
This  element  accumulates  in  the  external  tissues  of  the  plant  as 
a  constituent  of  the  inorganic  compound,  silica.  Oats,  and  corn 
through  three  generations,  have  been  matured  on  traces  of  silicon 
and  this  element  has  been  considered  generally  as  unessential  to 
plants.  There  is  considerable  evidence,  however,  that  this  ele- 
ment favors  economical  utilization  of  small  supplies  of  phospho- 
rus by  plants. 

Of  the  occasional  constituents  of  plant  ash,  manganese  has  been 
found  to  be  an  essential  constituent  of  laccase,  an  enzyme  in  the 
sap  of  the  lac-tree.  It  is  to  this  enzyme  that  the  setting  of  lacquer 
varnish,  is  due,  and  its  activity  has  been  found  to  be  proportional 
to  the  amount  of  manganese  present.  The  ash  of  laccase  contains 
as  high  as  2  per  cent  of  manganese. 

Aluminum  occurs  in  some  Lycopodiaceae  (club  mosses)  to  the 
extent  of  22  to  27  per  cent  of  the  ash.  The  recent  work  of  Mose- 
ley  on  the  occurrence  of  aluminum  in  certain  plants  is  of  great 
interest.  He  attributes  to  this  element  the  cause  of  the  disease 
known  as  "milk  sickness"  or  "trembles,"  which  may  break  out 
occasionally  among  dairy  cattle  and  other  animals.  Moseley  as- 
serts that  animals  contract  the  disease  when  fed  tin-  white  snake 


The  Plant.  10<> 

root,  which  he  showed  contains  aluminum  phosphate.  By  the 
use  of  this  salt  he  has  reproduced  the  disease  in  smaller  animals. 
The  occurrence  of  the  disease  in  the  southern  states  has  been 
traced  to  the  same  salt,  but  there  occurring  in  the  stems  of  the 
rayless  golden  rod.  In  fact,  Moseley  believes  that  wherever 
"trembles"  prevails  it  is  caused  by  aluminum  phosphate,  con- 
tained in  such  plants  as  the  white  snake  root  or  rayless  golden 

rod. 

Alpine  cress,  grown  where  the  soil  contained  over  20  per  cent 
of  zinc,  was  found  to  contain  the  following  amounts  of  zinc,  ex- 
pressed as  zinc  oxide  and  in  per  cent  of  the  total  ash : 

Roots 1 . 66  per  cent 

Stem  3.28       '« 

Leaf  13.12       " 

Iodine  occurs  in  marine  algae  to  the  extent  of  0.06  per  cent  of 
the  dry  matter.  This  is  of  interest  as  evidence  of  the  assimi- 
lating power  of  the  plant,  since  sea  water  contains  this  element 
to  the  extent  of  only  one  part  in  four  million. 

Bromine  also  occurs  in  sea  weeds.  Copper,  lead  and  other 
metals  are  sometimes  found  in  plants  growing  upon  soils  which 
contain  such  elements. 

Barium  has  been  found  in  beech  and  birch  trees  and  in  wheat 
grown  upon  barium-containing  soils.  The  presence  of  this  ele- 
ment as  an  ash  constituent  of  certain  leguminous  plants  has  been 
of  considerable  practical  concern  to  ranchmen.  It  has  been  shown 
to  be  the  active  constituent  of  certain  plants  producing  the  loco- 
disease  in  animals.  These  "  loco-weeds ",  as  they  are  common!}' 
called,  have  given  trouble  in  Australia,  and  losses  to  stockmen 
from  this  cause  on  the  United  States  plains  have  been  heavy.  The 
losses  in  Colorado  alone  have  been  estimated  at  a  million  dollars 
yearly.  Loco-plants  grown  on  some  soils  are  non-poisonous  and 
contain  no  barium.  This  is  a  case  in  which  an  accidental  ash 
constituent  has  become  of  marked  economic  importance. 

From  all  the  evidence  at  hand,  it  appears  probable  that  all 
the  ash  constituents  normally  present  in  plants  have  some  func- 


110  Agricultural  Chemistry. 

tion  in  the  chemical  processes  of  plant  growth.  In  this  connec- 
tion the  compound  phytin  is  of  interest.  This  is  a  complex  salt 
containing  potassium,  calcium  and  magnesium  in  combination 
with  an  organic,  phosphorus-bearing  acid.  It  has  been  isolated 
from  a  number  of  seeds,  including  the  common  cereals,  where  it 
represents  .a  concentrated  form  of  storage  of  ash  constituents  for 
the  embryonic  plant.  Phytin  may  influence  the  feeding  value  of 
these  seeds  and  their  products.  It  contains  practically  all  the 
phosphorus,  magnesium  and  potassium  occurring  in  wheat  bran 
and  gives  to  that  dairy  feed  its  laxative  properties. 


CHAPTER  VI 

/ 

FARM  MANURE 

For  a  soil  to  possess  fertility,  that  is,  to  be  able  to  properly 
;support  the  growth  of  plants,  certain  conditions  are  necessary. 
The  following  may  be  mentioned  as  being  perhaps  the  most  im- 
portant. 

(1)  Its  mechanical  or  physical  condition  must  be  suitable. 

(2)  It  must  contain  sufficient  plant  food  in  a  form  which  is 
readily  available  to  the  crop. 

(3)  It  must  not  contain  any  appreciable  quantity  of  poisonous 
or  injurious  substances. 

(4)  It  must  not  contain  injurious  insects,  fungi  or  other  or- 
ganisms which  are  destructive  to  crops. 

(5)  The  temperature,  sunshine,  rainfall  and  other  climatic 
conditions  must  be  suitable. 

Of  these  the  second  and -third  and  to  some  extent  the  first,  are 
matters  in  which  chemistry  may  be  of  service. 

Every  crop  removed  from  the  soil  robs  it  of  materials  which 
have  been  used  in  building  up  the  plant's  tissues.  Soil  which 
annually  bears  a  crop  must  in  time  become  exhausted  of  its  store 
of  plant  food  and  unfitted  to  bear  further  crops.  Often  one  con- 
stituent of  plant  food  becomes  exhausted  first  and  in  many  cases 
restoration  of  this  constituent  would  renew  the  fertility  for  some 
time  longer.  Substances  which  are  added  to  the  soil  in  order 
to  replace  the  ingredients  which  have  been  removed  by  previous 
crops  are  called  manures. 

All  constituents  of  plants  present  in  a  soil,  except  the  carbon, 
are  diminished  by  the  growth  of  crops  upon  it,  but  the  substances 
which  usually  first  become  deficient  are  combined  nitrogen,  and 
available  phosphorus,  calcium,  potassium  and  possibly  sulphur. 
Consequently  manures  are  valued  according  to  the  quantities 
of  those  ingredients  present  in  them,  although  in  many  cases  the 


112  Agricultural  Chemistry. 

other  constituents  may  exert  an  important  influence  upon  the 
soil. 

Barnyard  manure.  Of  all  fertilizers,  barnyard  manure  is  the 
oldest  and  still  the  most  popular.  It  consists  of  the  liquid  and- 
solid  excreta  of  the  farm  stock,  plus  the  litter  employed.  Early 
Roman  writers  called  atttention  to  the  fact  that  the  application 
of  the  excreta  of  farm  animals  resulted  in  increased  production, 
and  from  that  time  to  the  present  the  majority  of  farmers  have 
placed  their  reliance  on  this  class  of  manures  for  maintaining 
the  fertility  of  the  land. 

A  well  kept  manure  heap  may  safely  be  taken  as  one  of  the 
surest  indications  of  thrift  and  success  in  farming.  Neglect  of 
this  resource  causes  losses  which,  though  little  appreciated,  are 
vast  in  extent.  "  Waste  of  manure  is  either  so  common  as  to 
breed  indifference,  or  so  silent  as  to  escape  notice.  According 
to  recent  statistics  there  are  in  the  United  States  in  round  num-* 
bers,  19,500,000  horses,  mules,  etc.,  61,000,000  cattle,  47,000,000 
hogs  and  51,600,000  sheep.  Experiments  indicate  that  if  these 
animals  were  kept  in  stalls  or  pens  throughout  the  year  and  thq 
manure  carefully  saved,  the  approximate  value  of  the  fertilizing 
constituents  of  the  manure  produced  by  each  horse  or  mule  an- 
nually would  be  $27,  by  each  head  of  cattle  $20,  by  each  hog  $8j 
and  by  each  sheep  $2.  The  fertilizing  value  of  the  manure  pro- 
duced by  the  different  classes  of  farm  animals  in  the  Uniteij 
States,  would  therefore  be  for  horses,  mules,  etc.,  $526,500,000; 
cattle  $1,220,000,000;  hogs,  $376,000,000,  and  sheep,  $103,200,- 
000,  or  a  total  of  $2,225,700,000.  These  estimates  are  based  on 
the  values  usually  assigned  to  phosphoric  acid,  potash  and  nitroj 
gen  in  commercial  fertilizers,  and  are  possibly  somewhat  too  higll 
from  a  practical  standpoint.  On  the  other  hand  it  must  be  bornij 
in  mind  that  no  account  is  taken  of  the  value  of  manure  for  im- 
proving the  mechanical  condition  and  drainage  of  soils,  which  is 
fully  as  important  a  consideration  as  its  direct  fertilizing  value." 

It  is  fair  to  assume  that  at  least  one-third  of  the  value  of  the 
manure  is  annually  lost  through  careless  methods  of  manage- 


Farm  Manure. 


113 


ment.  And  this  estimate  is  conservative.  Even  at  this  figure 
we  have  the  tremendous  sum  of  $750,900,000  as  an  annual  loss 
in  the  United  States.  This  condition  is  the  more  unfortunate 
because  practically  all  of  it  could  be  prevented. 

In  Wisconsin  the  value  of  the  manure  produced  annually  by 
its  1,300,000  milch  cows,  1,100,000  other  cattle,  600,000  horses, 
1,000,000  sheep  and  1,900,000  swine,  based  on  the  above  figures, 
is  approximately  $60,000,000.  And  it  is  also  true  that  as  large 
a  proportion  of  its  valuable  constituents  is  annually  lost  as  in 
any  part  of  the  United  States.  It  is  safe  to  say  that  from  the 
farms  of  Wisconsin  there  is  an  annual  loss  of  at  least  $20,000,000 
from  the  indifferent  and  careless  management  of  the  manure 
produced. 

Composition  of  manure  from  different  animals.  The  manure 
produced  by  the  various  classes  of  farm  animals  differs  greatly 
in  its  composition  and  physical  properties.  The  following  table 
gives  the  average  composition  of  the  fresh  manure  (including 
solid  and  liquid  excrement)  of  farm  animals.  It  will  be  seen 
from  the  table  that  the  differences  in  composition  are  largely  due 
to  the  variations  in  the  amount  of  water  present: — 

Average  Composition  of  Fresli  Manures. 


Animal 

Water 

Nitrogen 

Phos.  Acid 

Potash 

Value 
per  ton 

Sll66p    • 

Per  cent 
64  0 

Per  cent 
0  83 

Per  cent 
0.23 

Per  cent 
0.67 

Dollars 
3.39 

Horse 

70  0 

0  58 

0.28 

0.53 

2.55 

Pig  

Cow 

73.0 

77  0 

0.45 
0  44 

0.19 
0.16 

0.60 
0.40 

2.14 
1.89 

Mixed 

75.9 

0  45 

0.21 

0.52 

2.08 

A  ton  of  mixed  manure  of  average  composition  contains  ap- 
proximately 5  pounds  of  phosphoric  acid,  10  pounds  of  nitrogen 
and  10  pounds  of  potash. 

Manures  containing  large  amounts  of  water  are  "cold  ma- 


J14 


Agricultural  Chemistry. 


nures ; ' '  that  is,  they  are  manures  which  heat  slowly  because  the 
high  water  content  checks  fermentations.  Sheep  and  horse  ma- 
nure are  known  as  "hot  manures, "  due  to  a  lower  water  content 
which  is  favorable  to  a  more  rapid  fermentation. 

Amount  and  value  of  manure  from  different  anitnals.  It  is 
sometimes  important  for  the  farmer  to  know  the  total  amount 
and  value  of  the  manure  produced  in  a  year  by  the  different  farm 
animals.  In  the  following  table  such  data  are  brought  together, 
with  the  amount  of  manure  calculated  to  the  same  live  weight 
of  the  various  animals. 

Amount  and  Value  of  Manure  per  1000  Ibs.  of  Live  Weight  of 
Different  Animals. 


Amount  per  day 

Value  per  day 

Value  per  year 

Sheep        

Pounds 
34  1 

Cents 
7  2 

Dollars 

•><)  01) 

Calves         

67  8 

6  7 

24.45 

Hogs 

56.2 

10  4 

37.96 

Cows  . 

74.1 

8.0 

29.27 

Horses 

48  8 

7.6 

27.74 

If  these  figures  are  accepted  as  representing  normal  conditions, 
it  follows  that  the  sum  of  thirty  dollars  may  be  taken  as  repi 
senting  the  average  value  of  the  fresh  manure  from  each  II 
pounds  of  live  weight.     The  use  of  this  factor  (thirty  dollars  pei 
1000  pounds)  will  enable  the  student  to  calculate  approximate!? 
what  the  nitrogen,  phosphoric  acid  and  potash  in  the  manui 
produced  on  his  farm  would  cost,*  if  purchased  in  commercial 
fertilizers,  granting  of  course  that  the  manure  is  so  managed  as 
to  prevent  loss  of  its  valuable  constituents. 


*A11  the  valuations  i^  the  calculations  made  are  based  on  15  cents  per 
pound  for  nitrogen  and  5  cents  per  pound  for  phosphoric  acid  and  for 
potash.  This  represents  in  round  numbers  the  market  price  of  these  in- 
gredients in  commercial  fertilizers  at  the  present  time. 


Farm  Manure. 


115 


Factors  which  influence  the  composition  of  manure.  The 
composition  of  the  excrement  varies  greatly,  dependent  on  the 
following  factors: 

(1)  The  character  of  the  ration. 

(2)  Age  and  kind  of  animal. 

(3)  Kind  and  amount  of  absorbents  used. 

Considerable  variation  in  the  composition  of  the  excreta  of 
various  animals  must  necessarily  be  expected. 

Influence  of  the  ration.  The  total  value  of  the  manure  pro- 
duced by  a  given  number  of  animals  is  dependent  on  the  quality 
and  quantity  of  the  feeding  stuffs  used  in  the  ration.  That  the 
different  materials  used  for  feeding  vary  greatly  in  their  fer- 
tilizing value  is  clearly  shown  in  the  following  table,  which  gives 
the  quantity  of  fertilizing  materials  in  one  ton  of  a  few  of  the 
common  feeding  stuffs  and  farm  products.  Additional  figures 
are  to  be  found  in  a  table  of  the  appendix: — 

Pounds  of  Fertilizing  Constituents  in  One  Ton. 


« 

Nitrogen 

Phosphoric 
Acid 

Potash 

Value 
per  ton 

Wheat  straw  

Lbs. 
11  8 

Lbs. 
2  4 

Lbs. 
10  2 

Dollars 
9  40 

Corn  Silage  

5.6 

2  2 

7  4 

1  32 

Clover  hav 

41  4 

7  6 

44  A 

Q    7Q 

Wheat  bran  

53  4 

57  8 

32  2 

12  52 

Linseed  meal  

108.6 

33  2 

27  4 

19  22 

Oats 

41  2 

16  4 

12  4 

7  62 

Milk 

10  0 

3  0 

3  0 

1  80 

Butter  

2.0 

1.0 

1  0 

0.4n 

Pigs  (live)  

40.0 

17.0 

3  0 

5  00 

The  figures  represent  the  fertilizing  values  of  the  different 
feeds,  provided  they  are  used  directly  as  manures.  It  is  clear 
that  the  richer  the  ration  is  in  nitrogen,  phosphoric  acid  and 
potash,  the  more  valuable  will  be  the  manure  produced  by  the 
animal.  It  is  necessary  now  to  inquire  what  proportion  of  the 
fertilizing  content  of  the  food  is  recovered  in  the  excrement. 


116  Agricultural  Chemistry. 

Influence  of  age  and  kind  of  animal.  If  a  mature  animal,  as 
a  steer,  for  example,  is  confined  in  such  a  manner  that  all  the 
excrement,  both  liquid  and  solid,  can  be  preserved,  it  will  be 
found  that  all  the  nitrogen,  phosphoric  acid  and  potash  of  the 
food  will  be  contained  in  the  excreta.  This  is  when  the  animal 
is  not  gaining  in  weight.  None  of  these  constituents  will  be  stored 
in  the  tissues,  but  all  are  voided  in  the  dung  and  urine.  On  the 
other  hand,  only  about  half  of  the  total  dry  matter  of  the  ration 
will  be  voided  in  the  excrement,  a  large  part  of  the  other  half 
having  been  given  off  from  the  lungs  as  carbon  dioxide.  While 
the  excreta,  therefore,  contain  only  about  half  of  the  total  dry 
matter  which  was  present  in  the  ration,  they  contain  all  the  con- 
stituents that  are  generally  considered  of  fertilizing  value. 

With  young  growing  animals,  gaining  in  weight,  the  above 
statement  is  incorrect.  They  retain  a  certain  proportion  of  the 
nitrogen,  potash  and  phosphoric  acid  for  use  in  building  up  their 
bodies.  The  amount  retained  depends  upon  the  age  of  the  animal 
and  its  rate  of  growth.  Experiments  indicate  that  calves  retain 
during  the  first  three  months  of  their  Jives  about  one-third  of  the 
fertilizing  value  of  the  food  consumed,  while  the  other  two-thirds 
would  be  found  in  the  excrement.  For  the  first  year  of  their 
existence  they  use  in  growth  about  one-fifth  of  the  nitrogen, 
phosphoric  acid  and  potash  present  in  the  food  and  as  the  animal 
ages,  the  amount  gradually  diminishes  until  practically  none  of 
these  materials  are  retained.  When  a  mature  animal  is  fatten- 
ing there  is  practically  no  drain  on  the  fertilizing  value  of  the 
feed,  provided  the  gain  is  all  fat.  This  is  due  to  the  fact  that 
fat  contains  only  carbon,  hydrogen  and  oxygen,  and  consequently 
its  production  does  not  remove  any  of  the  fertilizing  constituents. 

The  above  deductions  are  equally  applicable  to  the  other  classes 
of  farm  animals,  such  as  swine,  sheep  and  horses,  and  the  age  of 
the  animal  has  the  same  effect  on  the  value  of  the  manure. 

Influence  of  milk  production.  In  the  case  of  the  cow  another 
factor  is  introduced,  as  a  certain  proportion  of  the  nitrogen, 
phosphoric  acid  and  potash  is  removed  in  the  milk.  One  hundred 


Farm  Manure.  117 

pounds  of  milk  contain  on  an  average  about  0.53  pound  of  nitro- 
gen, 0.19  pound  of  phosphoric  acid  and  0.17  pound  of  potash. 
An  annual  yield  of  five  thousand  pounds,  therefore,  removes  in 
the  milk  fertilizing  material  amounting  in  value  to  $4.90.  If  the 
milk  is  sold,  this  is  lost  to  the  farm.  Where  butter  is  made  and 
sol'd,  practically  none  is  carried  away,  as  all  the  valuable  ingre- 
dients are  left  in  the  skimmed  milk.  The  fertilizing  value  of 
500  pounds  of  butter  amounts  to  about  ten  cents.  Even  when 
the  milk  is  sold,  fully  85  per  cent  of  the  manurial  value  of  the 
food  is  recovered. 

Eighty  per  cent  of  plant  food  recovered  in  manure.  Taking 
into  account  the  relation  between  matured  and  young  stock,  milk- 
producing  and  non-milk-producing  animals,  as  found  on  the 
average  farm,  it  is  conservative  to  assume  that  at  least  80  per 
cent  of  all  the  fertilizing  constituents  present  in  the  materials 
fed  on  the  farm,  is  voided  by  the  animals  in  the  solid  and  liquid 
excreta.  This  includes  the  amount  removed  in  the  milk,  that  re- 
tained by  the  young  animals  during  their  growing  period,  and 
consequently,  the  fertility  removed  from  the  farm  by  the  sale  of 
animals  grown  thereon.  The  fertilizing  value  of  the  excrement 
produced  from  one  ton  of  feeding  material  is  therefore  readily 
ascertained  by  taking  80  per  cent  of  the  fertilizing  value  therein 
stated.  From  this  it  will  readily  be  seen  that  the  composition 
of  the  feeding  stuff  really  determines  the  value  of  the  excrement. 
The  manure  (combined  solid  and  liquid  excrement)  from  one  ton 
of  wheat  straw  would  be  worth  $1.92,  while  that  from  one  ton  of 
corn  meal,  wheat  bran,  or  linseed  meal,  would  be  worth  $5.24, 
$10.01,  and  $15.37  respectively. 

Reference  to  the  table  will  show  that  in  most  cases  the  amount 
of  nitrogen  is  the  factor  determining  the  fertilizing  value  of  a 
feeding  stuff.  This  is  due  to  the  fact  that  nitrogen  is  usually 
present  in  larger  proportion  than  phosphoric  acid  or  potash,  and 
is  miich  more  costly  when  purchased.  Wheat  bran  and  linseed 
meal,  however,  are  particularly  rich  in  both  phosphoric  acid  and 
potash. 


118 


Agricultural  Chemistry. 


Effect  of  bedding  on  value  of  manure.  Barn  yard  manure, 
as  the  term  is  generally  used,  includes  in  addition  to  the  excreta, 
the  litter  or  bedding  used  to  absorb  the  urine.  The  following 
table  gives  the  composition  of  some  of  the  materials  used  for 
bedding : — 

Fertilizing  Constituents  in  One  Ton  of  Litter. 


Nitrogen 

Phosphoric  Acid 

Potash 

Wheat  straw  
Oat  straw 

Lbs. 
11.8 
12  4 

Lbs. 

2.4 
4.0 

Lbs. 
10.2 
24  8 

Clover  straw  

29.4 

8.4 

25.2 

Saw  dust 

4  0 

6.0 

14  0 

Peat 

20  0 

The  richer  the  bedding  the  more  valuable  will  be  the  manure. 
The  materials  commonly  used  for  bedding  are  low  in  the  elements 
of  fertility,  so  that  the  use  of  large  amounts  decreases  the  worth 
per  ton  of  the  manure,  but  in  any  case  sufficient  litter  should  bo 
used  to  absorb  all  the  liquid  excrement. 

Calculating  the  amount  of  manure  from  the  ration.  The  to- 
tal weight  of  manure  that  will  be  produced  from  the  material 
fed  an  animal  can  be  calculated  with  considerable  accuracy.  Ex- 
periments have  shown  that  about  50  per  cent  of  the  dry  matter 
present  in  the  ration  is  recovered  in  the  excrement.  The  least 
amount  of  bedding  that  will  absorb  all  urine  excreted  must  con- 
tain dry  matter  equal  to  25  per  cent  of  the  dry  matter  in  the 
feeds  used;  consequently  if  just  enough  bedding  is  used,  the 
manure  (excrement  plus  bedding)  contains  75  per  cent  of  the 
dry  matter  in  the  ration.  Since  mixed  farm  manure  contains  on 
an  average  75  per  cent  of  water,  or  25  per  cent  of  dry  matter,  the 
75  per  cent  of  dry  matter  mentioned  above  must  be  multiplied 
by  four  to  find  the  total  manure.  This  gives  a  result  of  300  pei 
cent  of  the  dry  matter  in  the  ration  for  the  weight  of  the  mam 
In  other  words  if  we  multiply  the  dry  matter  of  the  ration 
three,  we  will  have  a  close  approximation  to  the  weight  of  tl 


Farm  Manure .  119 

manure  produced.  This  method  of  calculating  holds  true  only 
when  the  theoretical  quantity  of  bedding  has  been  used. 

In  practice  the  farmer  usually  uses  all  the  bedding  material 
he  has  at  hand,  even  if  it  may  exceed  that  necessary  to  absorb  all 
the  urine,  and  such  practice  is  generally  considered  advisable  for 
the  reason  that  such  materials  as  straw  or  shavings  will  decay 
much  more  readily  when  mixed  with  the  excrement  of  animals. 
Where  more  litter  than  the  theoretical  amount  is  used,  the  method 
of  calculation  given  must  be  corrected  by  adding  to  the  total,  the 
weight  of  the  bedding  in  excess  of  25  per  cent  of  the  dry  matter 
of  the  ration. 

Value  of  manure.  The  great  importance  of  barn  yard  manure 
as  a  farm  resource  is  appreciated  to  its  full  extent  by  but  few 
farmers.  A  large  proportion  of  those  engaged  in  agricultural 
pursuits  seem  to  have  little  realization  of  the  immense  loss  in- 
curred through  the  waste  of  this  important  product  of  the  farm. 
They  begrudge  the  time  and  labor  required  to  remove  it  from 
the  barn  and  feeding  lot  and  it  is  not  uncommon  to  see  the  pur- 
chase of  commercial  fertilizers  and  the  waste  of  farm  manure 
going  on  at  the  same  time  and  on  the  same  farm.  Barns  are 
erected  on  steep  hillsides,  or  even  close  to  the  banks  of  running 
streams,  which  practice  insures  a  most  effective  and  wasteful  loss 
of  the  valuable  constituents  of  the  manure  heap. 

In  order  to  fully  emphasize  the  great  value  of  the  manure  pro- 
duced on  the  farm,  figures  are  given  for  the  amount  and  value 
of  the  manure  produced  in  one  year  by  a  herd  of  50  cows  giving 
an  average  individual  yield  of  15  pounds  of  milk  daily.  These 
results  are  largely  taken  from  Vivian's  "First  Principles  of  Soil 
Fertility." 

It  is  assumed  that  the  same  ration  is  fed  throughout  the  year. 
In  actual  practice  the  ration  varies  somewhat  throughout  the 
year,  but  nevertheless  the  good  feeder  aims  to  keep  the  composi- 
tion of  the  ration  very  much  the  same  even  when  various  sources 
of  food  materials  are  drawn  upon. 

The  following  ration  will  be  used  as  a  basis  for  calculation, 


120 


Agricultural  Chemistry. 


with  the  daily  consumption  for  a  cow  weighing  1,000  pounds  and 
giving  15  pounds  of  milk;  10  pounds  of  a  mixture  of  one-third 
each  of  corn  meal,  ground  oats  and  bran;  35  pounds  of  corn 
silage;  15  pounds  of  clover  hay  (medium  red).  This  is  a  good 
practical  ration  and  conforms  well  with  the  best  feeding  stand- 
ards. It  will  be  assumed  that  just  the  amount  of  wheat  straw 
which  would  theoretically  be  necessary  to  absorb  the  liquid  excre- 
ment is  used  as  bedding.  Allowance  for  milk  production  is  of 
course  made  by  using  the  factor  of  80  per  cent  as  the  basis  for 
calculating  the  amounts  of  fertilizing  material  recovered  in  the 
excrement  from  the  total  contained  in  the  feeds. 

Fertilizing  Constituents  of  the  Manure. 


Nitrogen 

Phosphoric  Acid 

Potash 

In  excrement  
In  bedding 

Lbs. 
8958.47 
742  .  6  1 

Lbs. 

3483.50 
340.22 

Lbs. 
7982.77 
974.28 

Totals 

9701.08 

3823.72 

8957.05 

The  prices  paid  for  fertilizing  materials  at  the  present  time 
are  15  cents  per  pound  for  nitrogen  and  5  cents  each  for  phos- 
phoric acid  and  potash.  These  prices  hold  only  when  raw  ma- 
terials are  bought,  and  much  higher  prices  are  paid  for  mixed 
fertilizers.  From  these  prices  is  calculated  the  total  value  of 
the  manure  produced  by  50  cows  in  one  year : 

Value  of  Manure  for  Fifty  Cows. 

Value  of  nitrogen $145;) .  1  s 

Value  of  phosphoric  acid 191 .19 

Value  of  potash 447.85 

Total  value  of  manure $2094  2 

This  means  that  the  fresh  manure  from  50  cows  contains 
amounts  of  nitrogen,  phosphoric  acid  and  potash  that  would  cost 
the  farmer  at  least  $2094.22  if  purchased  in  commercial  fertil- 


Farm  Manure.  121 

izers.  The  amount  of  manure  produced  would  weight  811.9  tons, 
giving  a  value  of  $2.58  for  each  ton.  How  near  the  actual  agri- 
cultural value  of  the  manure  will  approach  the  trade  value  will 
depend  upon  a  number  of  conditions,  such  as  crop  to  be  fed, 
physical  condition  of  the  soil,  climate,  and  especially  the  manage- 
ment of  the  manure  itself.  The  same  statement  applies  to  com- 
mercial fertilizers,  the  trade  price  being  no  indication  of  the 
agricultural  value  of  the  material,  and  the  farmer  who  profits 
most  from  the  use  of  commercial  fertilizers  is  also  the  one  to  be 
best  repaid  for  the  use  of  barn  yard  manure.  In  experiments 
conducted  at  the  Ohio  Experiment  Station  and  covering  a  period 
of  ten  years,  it  was  found  that  the  average  value  of  the  increase 
of  crop  produced  by  one  ton  of  fresh  manure  amounted  to  $3.44. 
If  50  cents  per  ton  be  allowed,  as  the  cost  of  applying  the  manure 
to  the  field,  there  still  remains  a  substantial  profit,  as  the  result 
of  the  application. 

How  to  increase  the  value  of  manure.  Where  a  system  of 
animal  husbandry  is  practiced,  the  farmer  will  find  that  the  most 
economical  way  to  increase  the  plant  food  for  the  farm  is  by 
purchasing  feeding  stuffs  rich  in  fertilizing  constituents,  feeding 
them  to  the  animals  and  using  the  manure  as  a  fertilizer.  In 
a  system  of  grain  farming  he  will,  of  course,  be  obliged  to  supply 
his  deficiency  in  plant  food  by  direct  purchase  of  the  needed 
elements  in  the  form  of  commercial  fertilizers.  The  successful 
stockman  finds  it  profitable  to  reinforce  the  feeds  raised  on  the 
farm  with  one  or  more  of  the  various  mill  and  other  by-products 
that  are  sold  as  cattle  feeds.  A  farmer  who  buys  large  quan- 
tities of  concentrates  is  increasing  the  fertility  of  his  land  pro- 
vided he  is  taking  proper  care  of  the  manure.  At  the  University 
Farm  there  is  an  annual  gain  in  fertilizer  elements  from  pur- 
chased feeding  stuffs  over  the  losses  sustained  by  the  sale  of  ani- 
mals and  animal  products. 

In  purchasing  feeding  stuffs,  one  should  always  consider  their 
fertilizing  value,  as  well  as  their  feeding  value,  for,  while  the 
substance  is  bought  primarily  to  feed,  it  is  sometimes  possible  to 


Li'i*  Agricultural  Chemistry. 

buy  different  materials  which  will  serve  practically  the  same  as 
feeds  and  yet  vary  greatly  in  their  value  as  fertilizers.  It  is  in- 
deed often  sane  practice  to  sell  some  of  the  products  produced 
on  the  farm  and  with  the  money  thus  obtained  purchase  other 
feeding  materials.  There  is  scarcely  a  farm  on  which  such  an 
exchange  could  not  be  made  to  advantage. 

The  following  example  will  illustrate  more  clearly  what  is 
meant.  At  the  time  of  writing  it  was  possible  to  buy  on  the 
local  market  6.4  tons  of  clover  hay  for  the  price  of  5  tons  oi 
timothy  hay,  and  5  tons  of  corn  could  have  been  exchanged  foi 
4.6  tons  of  wheat  bran.  Calculating  the  value  of  fertilizing 
materials  in  the  manner  already  described,  the  results  are 
follows : 

Fertilizing  value  of  6 A  tons  of  clover $  48.55 

Fertilizing  value  of  4 . 6  tons  of  bran 57 . 32 

Total $105  87 

Fertilizing  value  of  5  tons  of  timothy $  23.00 

Fertilizing  value  of  5  tons  of  corn 28  50 


Total $  51.50 

Gain  due  to  exchange s  f>4 .  :>7 

By  a  simple  exchange  of  products  without  any  cash  outlay  the 
fertilizing  value  of  the  ration  has  been  increased  $54.37  and  con- 
sequently the  manure  produced  would  have  been  worth  $43.49 
more  than  that  resulting  from  the  use  of  corn  and  timothy  hay. 
This  example  is  offered  merely  as  a  suggestion,  which  may  be 
made  of  considerable  practical  value,  dependent  on  the  market 
prices  of  the  various  feeds. 

In  the  above  example  the  actual  feeding  value  has  been  in- 
creased in  the  exchange  due  to  the  increase  in  protein  in  both 
clover  and  bran,  with  no  decrease  but  rather  an  actual  gain  ii 
the  dry  matter  purchased. 

Losses  in  manure.  Barn  yard  manure  is  a  perishable  product 
and  must  be  handled  with  intelligence  to  obtain  its  maximum 
v;i  hi'-.  1  )oubtless  as  manure  is  handled  on  the  majority  of  farms. 


Farm  Manure. 


12, '5 


only  one-half  of  its  worth  is  realized.  The  greatest  loss  is  through 
the  Avaste  of  the  liquid  excrement  by  the  use  of  insufficient  bed- 
ding to  absorb  it.  The  boring  of  holes  in  the  floor  for  the  express 
purpose  of  allowing  the  urine  to  run  off  as  rapidly  as  possible  is 
by  no  means  an  uncommon  practice.  The  following  table  gives 
the  composition  of  the  solid  and  liquid  excrement : 

Percentage  of  Fertilizing  Constituents  in  Solid  and  Liquid  Excrements 


Nitrogen 

Phosphoric  Acid 

Soda  and  Potash 

Solid 

Liquid 

Solid 

Liquid 

Solid 

Liquid 

Horses  

Per  cent 
.50 
30 

Per  cent 
1.20 
0.80 
0.30 
1.40 

Per  cent 
0.35 
0.25 
0.45 
0.60 

Per  cent 
Trace 
Trace 
0.12 
0.05 

Per  cent 
0.30 
0.10 
0.50 
0.30 

Per  cent 
1.50 
1.40 
0.20 
2.00 

Cows 

Swine  

60 
.75 

Sheep  

Pound  for  pound  the  liquid  excrement  is  more  valuable  than 
the  solid,  except  in  the  case  of  swine.  It  is  perfectly  safe  to  say 
that  of  the  total  fertilizing  material  in  the  manure,  two-thirds  of 
the  nitrogen,  four-fifths  of  the  potash,  and  practically  none  of 
the  phosphoric  acid,  are  found  in  the  urine.  It  is  apparent  that 
somewhat  over  half  of  the  total  value  of  the  manure  is  in  the 
urine.  Had  the  liquid  portion  of  the  manure  been  allowed  to 
run  away,  the  Value  of  the  excrement  as  calculated  in  the  example 
given  above  would  have  been  less  than  $1000  instead  of  $2049. 

Another  fact  of  great  importance  in  this  connection  is  that  the 
plant  food  in  the  urine  is  in  a  form  that  is  soluble  in  water  and 
consequently  more  available  to  plants  than  that  in  the  solid  dung. 
This  is  particularly  true  of  the  nitrogen.  The  solid  excrement 
consists  in  part  of  the  undigested  portion  of  the  food,  and  before 
its  nitrogen  can  become  available  to  plants,  it  must  undergo  de- 
composition and  decay. 

The  difference  in  value  of  the  solid  and  liquid  excrement  is 


124 


Agriculiu  ra I  Cli c  in  istry. 


well  brought  out  in  the  following  experiment  from  the  New  Jer- 
sey Experiment  Station.  Two  plots  were  treated  with  manure, 
the  one  receiving  only  solid  excrement,  while  on  the  other  the 
mixed  solid  and  liquid  excrement  was  used.  Each  plot  received 
enough  of  the  manure  to  supply  equal  quantities  of  nitroj 
The  results  are  stated  in  percentage  of  gain  over  a  check  pJ 
that  received  no  manure. 

Percentage  of  Gain  in  Yield  from  Manure. 


Solid  excrement  only 

Solid  and  liquid 
excrement 

First  year 

15  2 

52  7 

Second  year 

69  7 

116  9 

Third   year 

47  9 

80  6 

Average  .  . 

44  3 

83  4 

The  table  clearly  shows  that  the  yield  from  the  same  amounl 
of  nitrogen  was  very  much  larger  from  the  mixed  manure  than 
from  the  solid  excrement  alone.  The  experiment  also  indicates 
that  the  nitrogen  in  the  liquid  excrement  was  much  more  readily 
utilized  by  the  plant  than  that  in  the  solid  excrement. 

Manure  is  never  so  valuable  as  when  fresh ;  and  the  very  best 
methods  of  handling  and  care,  if  the  manure  must  be  stored,  can- 
not prevent  some  loss  of  the  valuable  constituents.  For  this 
reason,  it  is  advisable  when  possible,  to  apply  manure  to 
field  as  fast  as  it  is  made. 

Losses  in  manure  from  leaching.  In  addition  to  the 
losses  due  to  improper  absorption  of  the  urine,  the  manure  suffers 
heavily  from  leaching  by  rains.  This  is  probably  the  greatest 
source  of  loss.  It  is  often  allowed  to  lie  for  months  in  the  open 
barn  yard,  or  better,  directly  under  the  eaves  of  the  barn,  where 
the  leaching  and  washing  processes  are  more  complete.  Even 
after  plenty  of  litter  has  been  used  and  all  urine  absorbed,  it  is 


Farm  Manure. 


125 


not  uncommon  to  see  it  placed  where  it  is  directly  exposed  to 
the  continuous  action  of  the  elements. 

At  the  New  Jersey  Experiment  Station  four  samples  of  ma- 
nure were  exposed  to  the  weather  for  varying  lengths  of  time  and 
the  losses  determined.  The  results  are  given  in  the  following 
table : 

Losses  in  Manure  from  Leaching. 


Period  in  days 

Nitrogen 

Phosphoric  Acid 

Potash 

131 

Per  cent 
57  0 

Per  cent 
62  0 

Per  cent 

72  0 

70 

44  0 

16  0 

l>8  0 

76 

39  0 

63  0 

56  0 

50  

69.0 

59  0 

72.0 

Average 

51  0 

51   1 

61  1 

The  average  loss  amounted  to  more  than  50  per  cent  of  the 
value  of  the  manure  during  rather  short  periods.  It  is  very  com- 
mon, if  not  the  rule,  to  find  manure  exposed  on  many  farms  for 
longer  periods  than  here  shown.  The  aggregate  loss  of  the  plant 
food  of  the  country  by  such  exposure  is  appalling.  Experiments 
at  the  Cornell  Experiment  Station  with  manure  exposed  to  the 
weather  for  a  period  of  five  months  (April  to  September)  gave 
the  following  data: — 


Value  at  begin- 
ning per  ton 

Loss  per  ton 

Loss  per  cent 

Horse  manure  $2.80 
Cow  manure  2.29 

$1.74 
0.69 

62.0 
30.0 

It  is  necessary  to  state  that  the  losses  will  vary  with  climatic 
conditions.  During  heavy  rain  in  warm  weather,  the  losses  will 
be  heavier  than  in  dry  or  cold  weather. 

Losses  from  solid  excrement  by  leaching.  Not  only  is  the 
liquid  portion  of  the  excreta  of  the  animal  lost  by  exposure  to 


326 


Agricultural  Chemistry. 


leaching,  but  in  addition,  the  solid  excrement  suffers  loss.  A 
considerable  portion  of  both  the  phosphoric  acid  and  potash 
eliminated  through  the  intestine  is  in  a  soluble  form,  and  the 


Manure  leaching.     How  the  manure  in  America  is  wasted. 

Chemical  changes  constantly  going  on  in  a  manure  pile  are  mal 
ing  soluble  the  insoluble  nitrogenous  portions  of  the  dung. 

The  following  table  illustrates  the  losses  which  may  occur  wh< 
the  solid  excrement  alone  is  exposed  for  varying  lengths  of  tii 


Losses  in  Solid  Excrement  from  Leaching. 


Period  in  days 

•    •          •                 -            .-     .. 

Nitrogen 

Per  cent 
46  0 

Phosphoric  Acid 

Per  cent 

72  o 

70  . 

34  0 

97   0 

76  .... 

25  0 

54  o 



45  0 

42  0 

Average 

37  6 

Potash 

Per  cent 
80.0 
10.0 
48.0 
42.0 

47.1 


Farm  Manure. 


Per  cent  of  Gain  in  Yield  from  Manure. 


Fresh  Manure  Leached  Manure 


First  year                              .    ... 

52.7 

41.5 

Second  year                              .    .  . 

108.4 

96.8 

Third   year 

187.5 

89.6 

Average         

116.9 

76.0 

The  common  practice  of  open  yard  feeding,  where  the  manure 
produced  during  the  winter  is  spread  over  a  considerable  area 
and  often  allowed  to  remain  until  late  spring,  or  even  into  the 
fall,  is  most  wasteful  of  the  fertilizing  material  it  contains.  It  is 
safe  to  say  that  at  least  one-half  of  the  fertilizing  value  of  the 
manure  is  lost  by  such  practice.  This  method  of  feeding  is  ex- 
tremely common  and  in  the  corn  belt  of  this  country  it  is  not 
unusual  to  see  a  large  feeding  yard  covered  to  a  considerable 
depth  with  manure,  under  ideal  conditions  for  maximum  leach- 
ing. 

Losses  by  fermentation.  Manure  is  very  easily  decomposed 
and  the  losses  resulting  from  such  decomposition  fall  entirely  on 
the  most  valuable  constituent  of  the  manure,  the  nitrogen. 
Through  the  process  of  fermentation  no  potash  or  phosphoric 
acid  is  lost.  These  manurial  ingredients  are  wasted  only  through 
leaching. 


128  Agricultural  (Jhemistry. 

The  first  evidence  of  fermentation  is  the  odor  of  ammonia. 
This  is  noticeable  in  the  barn,  especially  if  it  has  been  closed 
during  the  night.  It  is  due  to  the  rapid  decomposition  of  urea, 
the  principal  nitrogenous  body  of  the  urine.  Ammonia  contains 
nitrogen  and  when  its  presence  is  noticed,  it  is  evident  that  nitro- 
gen is  escaping  into  the  air.  It  is  impossible  to  entirely  prevent 
the  formation  of  ammonia  from  the  urea,  but  it  is  possible  to 
greatly  reduce  its  loss  by  providing  plenty  of  absorbing  material 
and  keeping  the  manure  moist. 

The  fermentation  of  manure  is  due  to  different  kinds  of  bac- 
teria.    Some  of  these  can  exist  only  in  the  presence  of  air  an 
are  called  " aerobic,"  while  others  do  not  require  free  air  an 
are  classified  as  i(  anaerobic. "     The  aerobic  organisms  are 
sponsible  for  the  hot  fermentation  wrhich  is  the  cause  of  gre 
loss  of  value  in  manure.     It  is  well  known  that  when  manure 
thrown  into  loose  heaps  and  contains  a  large  proportion  of  ho 
or  sheep  excrement  it  soon  becomes  very  hot  and  dry,  in  fact,  h 
enough  to  steam,  and  the  temperature  may  reach  175°   Fah 
In  this  condition  the  common  "fire  fanging,"  or  burning  whi 
in  spots,  takes  place,  and  heavy  losses  of  nitrogen  are  sure  to 
cur.     Experiments  have  shown  losses  of  from  30  to  80  per  ce 
of  the  nitrogen.     In  extreme  cases  of  fire-fanging  all  the  nitro 
will  be  lost. 

If  the  manure  heap  is  so  compact  that  the  air  cannot  penetra 
it,  the  aerobic  bacteria  are  unable  to  live,  and  hence  hot  f ermen 
tion  is  prevented.     Where  aerobic  bacteria  are  active  the  solubl 
forms  of  nitrogen  in  the  manure  are  partly  converted  into  ni 
rates  and  these  in  turn  may  be  attacked  by  certain  anaerobi 
bacteria  called  "  denitrifiers, "  which  liberate  elemental  or  f 
nitrogen  from  such  compounds.     This  is  an  additional  reason  fo 
checking,  so  far  as  possible,  all  aerobic  fermentations.     The  pres 
ence  of  large  quantities  of  water  in  the  manure  heap  holds  t 
temperature  down,  displaces  the   air  and  in  this  way  chec 
aerobic  fermentations.     For  this  reason,  the  moist  cow  and  pi 
excrements  are  not  so  subject  to  hot  fermentation  as  that  of  t 


Farm  Manure.  129 

horse  or  sheep.  This  explains  the  sound  practice  of  mixing  the 
manure  from  the  various  classes  of  farm  animals,  when  it  is 
necessary  that  it  be  stored. 

When  the  manure  is  in  a  compact  mass  and  moist  the  fer- 
mentations that  take  place  are  due  to  anaerobic  bacteria.  These 
fermentations  convert  the  insoluble  plant  food  in  the  excrement 
into  soluble  forms,  with  little  loss  of  the  fertilizing  constituents. 
Under  the  best  conditions  of  care,  it  is  impossible  to  entirely  pre- 
vent losses  in  stored  manure,  although  if  properly  preserved  it 
may  be  reduced  to  about  10  per  cent  of  the  nitrogen  and  none 
of  the  other  two  fertilizing  constituents. 

Preservation  of  manure.  Saving  the  urine.  From  all  that 
has  been  said  it  must  appear  perfectly  plain  that  one  of  the 
greatest  losses  suffered  by  the  farm  is  through  failure  to  save  the 
liquid  excrement  of  the  animal.  To  insure  against  such  loss,  that 
part  of  the  barn  floor  on  which  the  excrement  falls  must  be  so 
tight  that  none  of  the  liquid  can  drain  away. 

The  trough  behind  the  animals  should  be  made  absolutely  tight 
by  the  use  of  pitch,  cement,  or  some  other  material  that  is  imper- 
vious to  water.  Besides  this  precaution,  enough  litter  should  be 
used  so  that  all  urine  is  absorbed  and  none  runs  away  by  drip- 
ping, when  the  manure  is  removed  from  the  barn.  It  is  often 
of  the  greatest  advantage  to  finely  cut  the  bedding  material. 
This  increases  its  absorbing  capacity,  and  facilitates  handling  the 
manure.  Straw  cut  in  one  inch  lengths,  for  example,  will  absorb 
about  three  times  as  much  urine  as  long  straw. 

Stockmen  who  have  practiced  cutting  the  bedding  assert  that 
the  great  ease  with  which  the  manure  will  be  removed  and  spread 
will  repay  the  cost  and  trouble,  to  say  nothing  of  the  saving  of 
bedding  materials. 

Use  of  preservatives.  As  has  been  previously  explained,  the 
urine  of  all  farm  animals  contains  its  nitrogen  principally  in  the 
compound  known  as  urea.  This  body  is  rapidly  and  readily  de- 
composed by  ferments  and  changes  into  ammonium  carbonate. 
This  latter  substance  is  volatile  and  passes  off  into  the  air,  where 


130  Agricultural  Chemistry. 

it  can  be  detected  by  the  sense  of  smell,  that  is,  by  the  odor  of 
ammonia.  The  dry  manures,  as  those  of  the  horse  and  sheep,  are 
particularly  subject  to  this  loss  of  nitrogen,  which  is  con- 
tained in  the  escaping  ammonia.  Many  from  the  farm  have 
suffered  with  "smarting  eyes"  when  removing  the  accumulated 
manure  from  the  horse  stable.  This  is  due  to  the  ammonia  and 
can  be  prevented  partly  by  the  use  of  land  plaster  or  gypsum. 
This  fixes  the  ammonia  in  part,  by  forming  ammonium  sulphate, 
which  is  a  non-volatile  body.  In  using  gj^psum  scatter  it  on  the 
floor  immediately  after  the  barn  has  been  cleaned  and  before  the 
fresh  bedding  has  been  spread.  From  one-half  to  one  pound  per 
animal  each  day  is  used  in  common  practice.  It  is  not  impossible 
that  part  of  the  beneficial  results  obtained  by  adding  gypsi 
in  the  manure  and  to  the  land  comes  from  the  additional  sup] 
of  sulphur. 

Other  preservatives,  as  kainite,  muriate  of  potash  and 
phosphate,  are  often  recommended  as  preservatives  for  mam 
and  to  prevent  the  loss  of  nitrogen.  They  are  reported  to 
injurious  to  the  hoofs  of  animals  and  when  used  should  be  scat- 
tered on  the  floor  and  carefully  covered  with  bedding.  There  is 
much  difference  of  opinion  as  to  their  merits  as  preservatives,  but 
unquestionably  they  all  can  effect  a  partial  retention  of  escaping 
ammonia  and  thus  act  as  "barn-sweeteners."  They  will  also 
serve  the  additional  function  of  reinforcing  the  manure  with  fer- 
tilizing materials.  They  may  be  used  in  the  same  quantity  as 
recommended  for  gypsum.  Dry  earth  has  been  recommended  i 
for  the  same  purpose  and  is  especially  useful  in  this  regard,  p{ 
ticularly  where  it  contains  a  large  amount  of  humus.  In 
parts  of  the  country  dry  peat  or  muck  soil  is  in  use  in  the 
in  connection  with  the  bedding.  It  should  never  be  used  in  qi 
tities  sufficient  to  make  the  manure  dry,  as  this  would  result 
still  greater  nitrogen  losses. 

Haul  the  manure  when  fresh.     Manure  is  never  so  valuable 
when  perfectly  fresh,  for  it  is  impossible  under  the  best  system  of| 
management  to  prevent  all  loss  of  its  fertilizing  ingredients.     Foi 


Farm  Manure.  131 

this  reason  it  is  recommended  that  wherever  possible,  the  manure 
should  be  hauled  directly  to  the  field  and  spread.  It  is  the  most 
economical  of  time  and  labor,  as  it  involves  handling  but  once. 
While  it  is  true  that  it  will  be  leached  by  the  rain,  nevertheless, 
the  soluble  portion  will  be  carried  into  the  soil,  where  it  is  desired 
to  have  it.  When  spread  in  a  thin  layer,  it  will  not  heat,  so 
there  will  be  no  loss  from  "hot  fermentation;"  and  where  ma- 
nure simply  dries  out  when  spread  on  the  ground,  there  is  no  loss 
of  valuable  constituents. 


Wherever  possible,  haul  and  spread  the  manure  daily  as  produced. 

Storing  manure.  When  it  is  impossible  to  remove  the  manure 
directly  to  the  field,  due  to  weather  conditions  or  lack  of  avail- 
able fields,  the  problem  of  properly  storing  it  will  present  itself. 
From  what  has  already  been  said,  it  is  apparent  that  the  two  in- 
jurious processes,  namely  leaching  and  hot  fermentation,  must 
be  prevented.  The  effect  of  leaching  may  be  prevented  in  two 
ways;  either  by  providing  water  tight  receptacles  so  that  the 
liquid  cannot  run  away,  or  by  keeping  the  manure  under  cover 
so  as  to  protect  it  from  the  rains.  The  first  method  is  in  general 
use  in  Europe,  where  pits  or  cisterns  of  cement  or  other  imper- 
vious material  are  built  and  in  which  the  manure  is  stored.  Some- 
times a  pump  is  provided,  whereby  the  liquid  portion  is  again 


132 


Agricultural  Chemistry. 


pumped  over  the  more  solid  portion,  keeping  it  moist  and  further- 
ing decay  with  minimum  loss.  This  process  makes  excellent 
manure  but  requires  time  and  labor.  The  more  economical  way 
for  the  American  farmer  to  prevent  leaching,  when  manure  mi 
be  stored,  is  to  keep  it  under  cover.  A  cheap  lean-to  or  shed 
all  that  is  needed.  Where  it  is  possible,  a  water-tight  floor  shoulc 

be  provided. 

Where  neither  cement  cistern  nor  covered  shed  is  available 

and  it  becomes  absolutely  necessary  to  store  the  manure,  the  hej 


When  the  manure  must  be  stored  and  there  is  no  cover,  build  the  pi 

as  shown  above. 

should  be  made  so  high  and  compact  that  the  hardest  rain  wi 
not  soak  through.     The  sides  should  be  perpendicular  and  tl 
top  dipped  toward  the  center.     It  is  advantageous  to  have 
manure  saturated  with  water,  but  large  losses  of  plant  food  we 
result  should  the  water  drain  away  from  the  heap. 

Hot  fermentation  can  be  controlled  by  keeping  the  manure  pi 
moist  and  compact.     These  two  conditions  exclude  the  air 
the  pile  and  prevent  the  action  of  that  class  of  bacteria  whic 
causes  hot  fermentation  and  in  addition,  require  free  oxygen 
their  activity.     When  the  heap  shows  a  tendency  to  dry  01 
water  should  be  added  and  each  daily  addition  of  manure  to 
pile  firmly  packed  into  place.     This  allows  decomposition  to 


Farm  Manure.  133 

tinue,  liberating  the  more  insoluble  plant  food  from  organic  con- 
stituents of  the  manure  and  greatly  improving  its  mechanical 
condition.  Mixing  the  manure  from  the  various  farm  animals 
is  the  very  best  practice.  The  drier  horse  and  sheep  manure  are 
checked  in  their  fermentation  by  the  more  moist  pig  and  cow 
excrements.  When  it  becomes  necessary  to  store  the  manure  for 
some  time,  it  is  recommended  to  cover  the  heap  with  an  inch  or 
two  of  earth.  This  prevents  the  escape  of  any  ammonia  that  may 
be  formed. 

Covered  sheds  save  manure.  Professor  Roberts,  formerly  of 
Cornell  University,  was  a  strong  advocate  of  covered  barn  yards 
for  the  conservation  of  manure.  They  are  simply  sheds,  with 
good  roofs,  with  or  without  sides  and  large  enough  to  allow  the 
cattle  to  freely  move  about.  The  bottom  is  made  tight  by  pud- 
dling clay  or  using  cement.  The  manure,  as  removed  from  the 
barn,  is  spread  about  and  sufficient  bedding  distributed  over  the 
surface  to  insure  cleanliness.  The  animals  trample  the  accumu- 
lating manure  into  a  compact  mass  and  keep  it  moist  by  their 
liquid  excrement.  This  insures  an  excellent  manure,  with  JDut 
slight  losses  of  plant  food.  In  addition,  it  affords  exercise  and 
a  healthful  environment  for  the  animals  in  severe  weather.  The 
plan  has  been  tried  by  many  dairymen  and  is  generally  consid- 
ered very  satisfactory.  It  is  said  that  the  cows  keep  cleaner  than 
when  stabled  and  that  the  milking  barn  is  in  a  more  sanitary  con- 
dition. 

The  throwing  of  cattle  and  horse  manure  into  basement  rooms 
to  be  worked  over  by  the  hogs,  is  from  the  standpoint  of  the  con- 
servation of  plant  food,  an  economical  process.  By  tramping 
and  working  over  the  manure,  and  by  adding  their  own  excre- 
ment, the  mass  is  kept  moist  and  fermentation  controlled. 

Deep  stall  manure.  In  some  parts  of  Europe  the  "deep  stall 
method  "  of  saving  manure  is  in  vogue.  It  consists  in  excavating 
the  stalls  where  the  cattle  stand  to  some  depth  below  the  barn 
floor  level.  Every  day  the  manure  is  spread  evenly  over  the  stall 
and  fresh  bedding  added.  The  excrement  and  bedding  are  firmly 


i:;i  Agricultural  Chemistry. 

packed  by  the  feet  of  the  animal  and  allowed  to  remain  through- 
out the  winter.  The  manure  produced  is  of  excellent  quality, 
but  for  sanitary  reasons  the  practice  is  hardly  commendable,  es- 
pecially in  the  case  of  dairy  cows. 

Composting  manure.  Where  well  rotted  manure  is  desired, 
as  in  market  gardening,  the  practice  of  composting  is  in  general 
use.  This  is  largely  done  to  avoid  the  deleterious  heating  effect 
that  would  result  from  applying  large  quantities  of  raw  manure. 
In  addition  it  is  sometimes  resorted  to  in  order  to  destroy  noxious 
weed  seeds.  A  favorite  method  with  some  market  gardeners  is 
to  compost  the  manure  with  earth,  peat,  or  muck.  This  is  done 
by  making  a  foundation  of  about  6  inches  of  dirt,  and  on  top  of 
this  placing  alternate  layers  of  manure  and  soil,  moistening  the 
mass  as  the  heap  grows.  The  mass  is  finally  covered  with  a  thin 
layer  of  earth  to  prevent  loss  of  nitrogen.  After  about  2  months 
the  pile  should  be  turned  over,  the  materials  well  mixed  and  more 
water  added,  if  necessary,  to  keep  the  compost  moist.  Sometimes 
sod  is  used  in  place  of  the  soil,  which  gives  a  fibrous  compost  very 
desirable  for  pot  and  bench  work.  Refuse  materials,  such  as 
kitchen  waste,  dead  animals,  etc.,  can  be  added  with  advantage 
to  the  compost  heap,  thereby  enriching  the  mass  and  disposing  of 
such  materials  without  the  production  of  offensive  odors.  Where 
further  enrichment  is  necessary,  it  is  good  practice  to  add  bone 
meal  or  rock  phosphate  (floats)  and  one  of  the  potash  salts  to 
the  heap.  Tn  this  way  the  plant  food  in  the  phosphates  is  made 
more  available  to  plants  and  the  compost  more  valuable. 

When  it  is  desired  to  produce  well  rotted  manure  in  a  v( 
short  time,  a  small  quantity  of  slaked  lime  can  be  mixed  with 
fresh  manure      This  occasions  a  rapid  decay  of  the  mass,  but 
it  also  entails  a  loss  of  more  or  less  nitrogen,  the  method  is 
to  be  recommended  for  general  use. 

Applying  manure.  A  manure  can  be  effective  only  when 
constituents  are  brought  into  contact  with  the  roots  of  the  crop.  | 
To  obtain  this  contact  to  its  fullest  extent,  the  manure  must  be 
thoroughly  ami  evenly  distributed  throughout  the  depth  of  the 


Farm,  Manure. 


135 


soil  mainly  occupied  by  the  roots.     For  this  reason  it  appears 

best,  when  possible,  to  apply  the  fertilizers  to  the  surface  as  a 
i  top  dressing,  in  order  that  the  soluble  plant  food  as  it  descends 
I  may  come  in  contact  with  the  plant  roots.  The  manure  to  be 
!  used  this  way  must  be  fine  or  well  rotted,  but  even  fresh  manure 
j  can  be  so  utilized  where  cut  straw  or  other  fine  material  has  been 

used  for  bedding.  The  practice  of  applying  the  manure  directly 
!  after  plowing  and  thoroughly  incorporating  it  with  the  soil  by 

the  use  of  the  harrow  or  cultivator  is  a  good  one. 

Spreading  the  manure  and  allowing  it  to  lie  on  the  surface 


A  poor  way  of  using  good  manure. 

should  be  practiced  only  on  level  fields  where  there  is  no  danger 
from  surface  washing.  It  has  been  claimed  that  when  manure 
is  spread  broadcast  and  allowed  to  lie  on  the  surface,  there  may 
be  serious  loss  of  ammonia  into  the  air,  but  experiments  have 
shown  that  loss  from  this  cause  must  be  very  small.  Manure 
made  during  the  winter  and  hauled  directly  to  the  field  and 
spread  on  areas  that  are  fairly  level,  whether  fall  plowed  or  on 
sod  to  be  turned  under  in  the  spring,  is  most  economical  of  labor 
and  conserves  most  efficiently  the  valuable  fertilizing  materials. 
It  may  even  be  spread  on  the  snow,  where  it  is  not  too  deep,  with- 
out serious  loss.  The  loss  is  certainly  less  than  when  thrown  in 
the  open  barn  yard. 

Manure  should  be  spread.  The  very  common  practice  of 
hauling  manure  to  the  field,  there  to  be  thrown  into  heaps,  has 
several  serious  objections.  In  the  first  place  it  increases  the 
work  entailed  in  spreading,  as  it  must  be  handled  twice.  When 


136 


Agricultural  Chemistry. 


manure  is  so  piled  there  is  danger  of  injurious  fermentations, 
with  consequent  losses  of  nitrogen.  In  addition,  the  leaching 
from  such  piles  increases  the  amount  of  plant  food  directly  be- 
neath and  hence  produces  a  rank  growth.  It  is  not  uncommon 
to  lind  the  next  season 's  crop  spotted  by  a  more  luxuriant  growth 
and  deeper  green  color  on  the  areas  where  the  manure  heaps  havt 
been  placed.  This  condition  is  highly  undesirable,  as  it  cai 
the  crop  to  mature  at  different  ages  and  also  endangers  loss 
lodging.  A  crop  with  a  large  plant-food  supply  will  have 


Uneven  grain  and  grass.     This  bad  condition  comes  from  leaving  the 
manure  in  small  piles.     It  should  be  spread  when  hauled. 

longer  season  of  growth  than  one  with  a  meagre  supply.  If  the 
manure  is  spread  directly  from  the  wagon,  the  danger  of  uneven- 
ness  of  growth  is  largely  avoided  and  the  cost  of  labor  reduced. 
When  very  coarse  manure  is  used,  it  is  advantageous  to  supple- 
ment the  spreading  from  the  wagon  by  the  use  of  a  drag  tl 
will  break  up  the  larger  lumps  and  thus  spread  it  more  uni- 
formly. 

Depth  to  cover  manure.  Where  the  manure  is  so  coarse  as 
interfere  with  tillage,  it  will  become  necessary  to  plow  it  under. 
Judgment  must  be  exercised  as  to  the  depth  to  which  it  shouk 
be  covered.  As  a  general  rule,  it  should  not  be  so  deep  as 
prevent  access  of  air  and  moisture,  which  are  necessary  to  ii 


Farm  Manure.  137 


fermentation  and  nitrification.  In  clay  soils  it  is  possible  to 
bury  the  manure  so  deeply  as  to  prevent  decay,  while  in  open 
sandy  soils  this  danger  is  not  so  great.  In  very  compact  soils  it 
has  been  recommended  that  the  depth  should  not  exceed  4  inches. 
During  very  dry  seasons  much  harm  may  result  from  plowing 
under  large  amounts  of  coarse  manure,  as  there  may  not  be  suf- 
ficient moisture  in  the  soil  to  bring  about  the  decay  of  the  organic 
matter.  This  undecayed  material  may  result  in  a  physical  in- 
jury to  the  soil. 

Applied  to  sod.  A  practice  that  is  highly  recommended  is  to 
apply  the  manure  as  it  is  made  to  meadow  or  sod  land  that  is 
to  be  plowed  and  planted  the  following  spring.  In  this  way  what 
is  applied  in  summer  or  early  fall  is  partly  used  by  the  growing 
crop,  thus  avoiding  losses,  and  when  the  sod  is  plowed  under  the 
entire  plant  food  can  be  used  by  the  succeeding  crop.  Manure 
applied  to  pasture  or  meadows  during  the  summer  or  fall  aids 
in  conserving  the  moisture  by  its  action  as  a  mulch,  as  well  as 
supplying  plant  food  and  inducing  a  longer  season  of  growth. 

Fresh  and  rotted  manure.  The  form  in  which  manure  should 
be  applied  is  determined  largely  by  the  soil  on  which  it  is  to  be 
used.  On  heavy  soils  containing  large  amounts  of  clay,  more 
benefit  will  be  derived  from  fresh  manures  than  from  those  that 
are  well  rotted.  The  fresh  manure  warms  these  cold  soils,  makes 
them  more  porous,  and  the  fermentations  that  take  place  during 
decay  tend  to  make  the  soil  more  mellow. 

On  light  or  sandy  soils,  on  the  other  hand,  those  manures  that 
are  well  rotted  will  be  found  most  beneficial.  Such  soils  are 
likely  to  suffer  from  the  drying  and  heating  effect  of  raw,  coarse 
manure,  and  to  have  their  porosity  increased  to  an  undesirable 
extent.  "While  it  is  doubtful  if  moderate  quantities  of  fresh  ma- 
nure are  seriously  injurious  to  these  soils,  nevertheless,  if  applied 
in  large  quantities,  it  is  much  safer  to  have  the  manure  well 
rotted.  It  will  then  improve  the  mechanical  condition  of  the  soil 
and  increase  its  water  retaining  power. 

Fresh  manure  has  a  forcing  effect  and  tends  to  produce  stems 


13S  AgriniUural  Chemistry. 

and  leaves  at  the  expense  of  fruit  and  grain.  It  is  therefore 
better  for  early  garden  truck,  grasses  and  forage  plants  than  for 
cereals  or  fruits.  Corn  is  usually  benefited  by  liberal  applica- 
tions of  fresh  manure.  In  fact  it  may  be  said  that  when  in  doubt 
as  to  where  to  appty  the  manure, ' '  use  it  on  corn. "  It  is  claimed 
that  fresh  manure  is  injurious  to  sugar  beets  and  tobacco,  pro- 
ducing a  large  beet  of  low  sugar  content  and  a  coarse  and  un- 
desirable tobacco  leaf.  It  is  a  well  known  fact  that  raw  manure 
in  large  quantities  is  likely  to  cause  lodging  with  the  small  grains, 
such  as  barley,  oats  and  wheat.  In  the  case  of  sugar  beets,  ex- 
periments with  fresh  manure  at  the  New  York  State  Experiment 
Station  have  given  beets  of  high  sugar  content  and  without  rank 
leaf  growth,  results  at  variance  with  those  of  European  experi- 
ments. Climate  and  soil  are  probably  very  important  factors  in 
determining  what  will  be  the  comparative  results  with  the  two 
kinds  of  manure. 

Instead  of  using  the  manure  directly  on  the  small  grains,  it 
,       is  good  gractice.  where  corn  is  grown,  to  apply  it  liberally  to  that 
crop  and  plant  the  field  to  the  smaller  grains  the  following  year. 
"When  this  is  done  the  danger  from  rank  growth  is  minimized. 

Rate  of  application.  As  to  the  rate  at  which  manure  should 
V  be  applied,  no  fixed  rule  can  be  given.  It  will  depend  upon  the 
character  of  the  soil,  the  quality  of  the  manure,  the  nature  of 
the  crop  and  the  frequency  of  application.  German  authorities 
consider  7  to  10  tons  light,  and  20  tons  or  more  heavy,  applica- 
tions. Sir  Henry  Gilbert  considered  14  tons  per  acre,  annually, 
excessive  for  wheat  and  barley.  For  ordinary  farm  crops  it  is 
not  customary  to  use  more  than  8  to  10  tons  per  acre.  As  a  gen- 
eral principle  it  may  be  stated  that  frequent  light  dressings  pay 
better  than  very  large  ones  at  long  intervals.  Too  liberal  appli- 
cations are  wasteful.  The  amount  of  manure  produced  on  1h« 
average  farm  is  so  small  compared  with  the  land  to  be  fertilized 
that  it  would  be  utterly  impossible  to  spread  it  over  all  the  farm 
yearly.  For  this  reason  it  is  considered  good  practice  to  apply 
tl"'  manure  to  one  crop  in  a  rotation,  thus  covering  only  part  of 


Farm  Manure. 


139 


the  farm  each  year.  The  following  three-year  plan  of  rotation 
will  explain  the  above  statement;  corn,  1  year;  grain,  1  year; 
clover,  1  year ;  the  manure  is  applied  to  the  clover  sod.  The  fol- 
lowing table  brings  out  clearly  the  relation  of  plant  food  removed 
by  such  a  rotation  as  described  above,  and  the  quantity  returned 
by  the  application  of  10  or  15  tons  of  farm  manure  of  average 
composition  once  in  3  years.  No  account  is  taken  of  losses  by 
drainage  or  the  gain  in  nitrogen  to  the  soil  of  probably  50  pounds 
per  acre,  by  the  growth  of  the  clover. 


Wt,  crop 

Phos- 

dry 

Nitrogen 

phoric 

Potash 

per  acre 

Acid 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Corn  grain  30  bushels  

1500 

28  0 

10.0 

6.5 

Corn  stalks 

1877 

15.0 

8  0 

29.8 

Barley  grain  40  bushels 

1747 

35.0 

16  0 

9.8 

Barley  ^traw 

2080 

14.0 

4  7 

25.9 

Red  clover  2  tons  

3763 

98. 

24.9 

83.4 

Total  removed 

190.0 

63.6 

155.4 

Manure  10  tons 

100.0 

50.0 

100.0 

Manure  15  tons 

150.0 

75.0 

150.0 

"We  see  from  this  table  that  it  would  require  once  in  3  years 
the  application  of  about  15  tons  of  manure  of  average  composi- 
tion to  replace  the  plant  food  removed  by  the  three  crops. 

Relation  of  manure  to  maintenance  of  fertility.  At  the  Rot- 
hamsted  Experiment  Station,  England,  experiments  to  determine 
the  relative  value  of  farm  yard  manure  and  commercial  fertilizers 
have  been  carried  on  over  a  very  long  period  of  time.  On  certain 
plots,  crops  have  been  grown  continuously  with  no  fertilizer,  on 
other  plots  with  barn  yard  manure  at  the  rate  of  14  tons  per  acre 
annually,  and  on  still  others,  various  combinations  of  commercial 
fertilizers  have  been  tested.  The  tests  extend  over  40  years  and 
are  given  in  the  following  table  as  averages  of  five  8-year  periods. 


140  Agricultural  Chemistry. 

Comparative  Effect  of  Manure  and  Commercial  Fertilizers. 


Barley—  Bushels  per  acre  | 

Wheat-  -Bushels  per  acre 

No 
Manure 

Manure 

Com- 
mercial 
Fer- 
tilizers 

No 
Manure 

Manure 

Com- 
mercial 
Fer- 
tilizers 

1st  8  years  
2nd  8  years  
3rd  8  years  
4th  8  years 

24 
18 
14 
14 
11 

16 

44 
52 
49 
52 
44 

48 

48 
51 
45 
42 
41 

45 

16 
13 
12 
10 
.  12 

13 

34 
35 
35 

28 
39 

34 

36 
39 
36 
32 

38 

36 

oth  8  years 

Average  (40  years) 

It  will  be  seen  that  there  was  practically  no  difference  between 
the  plots  dressed  with  farm  manure  and  those  receiving  commer- 
cial fertilizers.  In  fact  the  test  was  hardly  fair  to  the  manure, 
as  excessive  quantities'  of  commercial  fertilizers  were  applied. 
The  amount  of  nitrogen  added  to  the  wheat  was  equal  to  that 
contained  in  800  pounds  of  nitrate  of  soda,  an  excessive  amount. 
It  is  believed  by  some  authorities  that  had  the  experiment  been 
conducted  in  America  the  result  would  have  been  more  favorable 
to  the  barn  yard  manure.  This  judgment  is  based  on  the  belief 
that  nitrification,  due  to  the  influence  of  climate,  would  be  more1 
rapid  in  this  country  than  in  England. 

Lasting  effect  of  manure.  Barn  yard  manure,  because  of  its 
slow-decomposing  organic  matter,  has  a  lasting  effect  when  ap- 
plied to  the  soil.  Where,  at  Rothamsted,  a  plot  was  manured  an- 
nually for  20  years,  and  then  received  no  manure  for  the  next 
20  years,  this  effect  is  clearly  shown.  The  following  table  illus- 
trates this  effect.  The  figures  represent  the  action  of  the  residual 
manure,  as  no  fertilizer  was  added  during  the  period  covered  by 
the  table.  The  crop  grown  was  barley  and  is  expressed  in  bush- 
els per  acre. 


Farm  Manure. 
Lasting  Effect  of  Manure. 


141 


Unmannred 

Effect  residual 
manure 

First       five  years.    .    . 

13 

39 

Second   five  years  
Third     five  vears.    .    .       

14 

14 

29 
30 

Fourth   five  veais     

12 

23 

Average  (20  years)  

13  '2 

30 

The  table  shows  that  the  effect  of  the  manure  was  perceptible 
in  yield  for  at  least  20  years  after  the  last  application.  In  fact 
the  value  of  barn  yard  manure  cannot  be  estimated  on  the  basis 
of  the  plant  food  it  contains  alone.  It  has  a  greater  value  than 
that  because  of  its  improvement  on  the  physical  conditions  of  the 
soil  and  the  increased  fermentations  which  result  from  its  ap- 
plication. It  is  always  a  safe  fertilizer  for  the  inexperienced 
farmer,  as  there  is  little  danger  of  lasting  injury  from  its  use, 
while  it  is  possible  to  use  commercial  fertilizers  in  such  a  way 
as  to  make  the  soil  poorer  after  their  use  than  it  was  before. 

Effect  of  style  of  farming  on  fertility.  Prominent  authorities 
in  agriculture  believe  that  in  a  system  of  strictly  animal  hus- 
bandry, where  nothing  is  sold  from  the  farm  except  animals  or 
animal  products,  and  all  the  manure  properly  saved  and  utilized, 
the  fertility  of  the  land  may  be  maintained  indefinitely  without 
the  purchase  of  commercial  fertilizers.  It  should  be  remembered 
that  a  positive  balance  of  plant  food  could  not  be  maintained  in 
this  way  unless  additional  feeding  materials  were  purchased  and 
fed  on  the  farm.  This  is  due  to  the  20  per  cent  loss  of  fertilizing 
materials  contained  in  the  growing  animals  and  milk  produced. 
While  there  may  be  large  stores  of  potential  plant  food  in  the 
soil  which  could  make  up  the  20  per  cent  yearly  deficit  and  main- 
tain average  crop  production,  nevertheless,  a  permanent  agri- 
culture could  not  be  founded  on  such  practice. 

In  systems  of  animal  husbandry  it  is  the  rule  to  purchase  ad- 


1   |L' 


Agricultural  Chemistry. 


ditional  feeding  stuffs.  The  amount  of  wheat  bran  necessary  to 
offset  the  losses  on  a  farm  from  which  live  stock  and  milk  are 
sold,  is  shown  in  the  following  table.  The  calculations  are  based 
on  what  a  farm  of  160  to  200  acres  could  do.  Only  potash  ana 
phosphoric  acid  are  considered,  as  the  supply  of  nitrogen  for 
plant  production  can  be  maintained  through  the  growth  of  legu- 
minous crops. 

Compensation  of  Losses  on  a  Farm  by  Purchase  of  Wheat  Bran. 


Potash 

Phosphoric  Acid 

Live  stock  sold  

Lbs. 
20,000 

Lbs. 
40 

Lbs. 
300 

Milk  sold  

1  46,  000 

250 

262 

Total  

290 

562 

Bran  Purchased  

18,000 

306 

630 

The  table  brings  out  the  fact  that  9  tons  of  wheat  bran  would 
offset  the  losses  sustained  by  the  sale  of  farm  animals  and  milk. 
Where  cream  is  sold  instead  of  milk,  the  amount  of  wheat  bran 
necessary  to  supply  the  loss  of  potash  and  phosphoric  acid  in  the 
stock  sold  would  be  about  5  tons. 

It  must  be  clear  to  the  student  from  what  has  already  been 
said,  that  losses  in  fertility  are  greater  in  any  system  of  farming. 
where  the  crops  are  sold  from  the  farm  than  when  some  form  of 
animal  husbandry  is  followed,  especially  if  no  commercial  fer- 
tilizers are  purchased.  To  illustrate  this  point  more  fully,  the 
following  table  adapted  from  a  Minnesota  bulletin  is  given.  Four 
farms,  each  containing  160  acres,  were  assumed.  On  the  first 
nothing  but  grain  was  raised  and  sold.  The  second  was  about 
'•'jually  divided  between  grain  and  stock  farming,  and  the  third 
and  fourth  were  devoted  exclusively  to  stock  raising  and  dairy- 
ing, respectively.  In  the  last  two  cases  a  small  amount  of  the 
farm  produce  was  exchanged  for  mill  products,  which  accounts 


Farm  Manure. 


143 


for  the  slight  gain  in  phosphoric  acid,  but  it  was  assumed  that 
no  other  concentrates  or  fertilizers  were  purchased.  The  de 
cidedly  smaller  loss  of  nitrogen  on  the  second  farm  and  the  actual 
increase  of  nitrogen  on  the  stock  and  dairy  farms  are  due  to 
fixation  of  nitrogen  from  the  growth  of  clover.  The  figures  rep- 
resent pounds  of  fertilizing  material  lost  or  gained  on  the  farm 
in  1  year. 

Effect  of  Style  of  Farming  on  Fertility. 


Kind  of  farming 

Gain  or  loss  infertility 

Nitrogen 

Phosphoric  Acid 

Potash 

All  grain 

Lbs. 
-5600 
-1100 
+1100 
-1-1200 

Lbs. 
-2500 
-1000 
-h    50 

+    75 

Lbs. 
-4200 
-1000 
•    (50 

-     85 

Mixed  

Stock 

Dairy 

Green  manuring.  The  lowered  crop  producing  power  of  a  soil 
is  in  many  instances  due  to  the  rapid  decrease  in  the  amount  of 
humus  which  it  contains.  Humus  is  formed  in  most  cases  from 
the  plants  which  have  previously  grown  on  the  field  and  have 
later  become  a  part  of  the  soil.  It  may  be  produced  from  animal 
or  vegetable  material  added  as  manure.  Virgin  soils  are  rich  in 
humus,  but  continued  cropping  with  no  provision  for  maintaining 
the  supply  may  result  in  its  being  decreased  from  one-third  to 
one-half  in  a  period  of  not  more  than  15  years.  Humus  is  of  im- 
portance because  it  is  a  storehouse  of  plant  food,  especially  nitro- 
gen. Most  of  the  nitrogen  of  the  soil  is  contained  in  the  more 
or  less  decomposed  organic  matter  present. 

Plowing  under  green  crops,  grown  for  that  purpose,  is  one  of 
the  oldest  means  of  increasing  the  humus  content  of  soil.  By 
this  practice,  not  only  is  the  soil  enriched  with  carbonaceous  mat- 
ter derived  from  the  air,  but  a  considerable  amount  of  nitrates 
which  would  have  been  formed  by  nitrification  during  the  growth 


144 


A  gricultura  I  Chemistry. 


of  the  crop,  is  assimilated,  converted  into  complex  organic  com- 
pounds in  the  plant  and  restored  to  the  soil.  Without  the  crop 
these  nitrates  would  have  been  to  a  large  extent  lost  by  drainage. 
The  planting  of  "catch  crops"  for  this  purpose  is  best  done  in 
the  autumn,  since  nitrification  is  then  very  rapid  and  loss  from 
washing  out  of  nitrates  by  winter  rains  is  to  a  great  extent  pre- 
vented. 

For  green  manuring,  two  classes  of  crops  are  in  common  use. 


Experiments  showing  that  "green  manuring"  with  legume  plants  can 
supply  all  the  nitrogen  needed  by  a  succeeding  crop  (after  Wagner). 

To  the  first  class  belong  such  crops  as  buckwheat,  mustard,  rye, 
rape,  etc.  These  kinds  of  plants  are  efficient  in  restoring  car- 
bonaceous matter  and  what  nitrogen  was  available  for  their 
growth.  They  have  added  no  essential  element  of  plant  growth. 
They  should  be  plowed  under  before  seed  is  produced  or  other- 
wise the  land  would  be  fouled  for  the  next  year. 

To  the  second  class  belong  the  legumes.  They  have  all  the  ad- 
vantages of  the  first  class,  but  in  addition,  increase  the  amount 
of  nitrogen  in  the  soil.  Those  most  often  recommended  are  red 
clover,  the  lupines,  cow  peas,  crimson  clover,  soy  bean  and  the 


Farm .  Manure .  145 

ordinary  field  bean  and  field  pea.  Red  clover  in  the  one  most 
commonly  used.  They  produce  good  results  even  when  the  crop 
is  harvested  and  the  stubble  plowed  under.  At  the  Rothamsted 
Experiment  Station  it  has  been  estimated  that  50  pounds  or  more 
of  nitrogen  per  acre  is  added  to  the  soil  annually  in  the  roots  and 
stubble  of  clover  alone. 

Under  certain  conditions  green  manuring  may  be  attended  by 
dangers.  In  a  dry  season  the  growth  of  a  crop  to  plow  under 
may  decrease  the  moisture  content  of  the  soil  to  a  point  that  is 
harmful  to  the  succeeding  crop.  In  such  a  season  there  may  also 
be  insufficient  moisture  in  the  soil  to  bring  about  the  decomposi- 
tion of  the  organic  matter  which  is  turned  under.  When  green 
manuring  is  practiced  in  a  dry  season,  the  land  should  be  rolled 
so  as  to  establish  capillarity  as  far  as  possible. 

Where  systems  of  stock  farming  are  practiced,  it  appears  to 
be  a  wasteful  method  to  plow  under  green  crops  which  may  be 
suitable  for  feed.  It  would  be  found  more  profitable  to  feed  them 
to  the  animal,  carefully  save  the  manure  and  return  it  to  the 
fields.  Green  manuring  will  prove  desirable  in  any  system  of 
farming  where  the  crops  are  sold  from  the  farm.  On  the  other 
hand,  when  the  farmer  is  engaged  in  stock  farming  and  the  crops 
are  of  value  as  feeds,  then  turning  them  under  must  be  considered 
a  wasteful  practice. 


CHAPTER  VII 
COMMERCIAL  FERTILIZERS 

It  is  neither  possible  nor  necessary  for  all  farmers  to  engage 
in  stock  raising  or  dairying  in  order  to  maintain  the  fertility  of 
the  land.  While  it  is  possible,  as  has  been  described,  to  main- 
tain without  the  purchase  of  commercial  fertilizers,  a  positive 
balance  of  plant  food  on  the  farm  in  the  practice  of  the  above 
systems,  it  is  manifestly  impossible  to  do  so  in  a  system  of  grain 
farming  where  the  crops  raised  are  all  sold  from  the  farm.  In 
the  latter  system  recourse  to  commercial  fertilizers,  supplemented 
by  green  manuring  for  the  purpose  of  maintaining  the  humus 
content  of  the  soil,  must  be  made  sooner  or  later. 

At  the  present  time  probably  $60,000,000  are  spent  annually 
in  the  purchase  of  fertilizers  in  the  United  States,  and  it  is  no 
exaggeration  to  say  that  fully  one-half  of  this  is  money  thrown 
away.  This  is  not  an  argument  against  their  use,  but  simply 
means  that  they  should  be  purchased  with  judgment  and  not 
used  at  all  until  actual  investigation  has  shown  them  to  be 
necessary. 

Plant  food  not  the  only  factor  in  crop  growth.  It  should  be 
remembered  that  other  factors  than  plant-food  supply  enter  into 
the  production  of  large  crops.  Improper  physical  condition  of 
the  soil,  lack  of  moisture,  deficiency  of  humus,  unsuitable  soil 
reaction,  unfavorable  weather,  etc.,  all  may  interfere  with  the 
normal  and  vigorous  development  of  the  plant  and  thus  cause 
diminished  crop  returns,  even  when  the  plant  has  within  reach 
all  the  food  it  needs.  These  unfavorable  conditions  may  partly 
be  ameliorated  through  means  available  to  man,  such  as  drain- 
ing, irrigating,  harrowing,  liming,  etc.  Too  frequently  fertil- 
izers are  made  to  take  the  place  of  tillage  when  they  should  be 
used  to  supplement  it.  That  is,  fertilizers  are  more  likely  to 
give  profitable  results  when  used  in  conjunction  with  an  excel- 


Commercial  Fertilizers.  147 

lent  physical  condition  of  the  soil,  and  the  man  who  would  ob- 
tain best  results  without  fertilizers  is  the  one  most  likely  to 
realize  a  profit  from  their  use.  ' '  The  fact  that  fertilizers  can  now 
be  easily  secured,  and  the  ease  of  application,  have  encouraged 
a  careless  use,  rather  than  a  thoughtful  expenditure  of  an  equiv- 
alent amount  of  money  or  energy  in  the  proper  preparation  of 
the  soil.  Of  course  it  does  not  follow  that  no  returns  are  secured 
from  plant  food  applied  under  unfavorable  conditions,  though 
full  returns  cannot  be  secured  under  such  circumstances.  Good 
plant  food  is  wasted  and  the  profit  possible  to  be  derived  is 
largely  reduced. ' '  Again,  in  many  instances,  the  ease  with  which 
commercial  fertilizers  can  be  secured  tends  to  a  neglect  of  the 
home  resources  and  one  far  too  commonly  sees  the  waste  of  farm 
manure  and  the  purchase  of  commercial  fertilizers  practiced  on 
the  same  farm. 

What  commercial  fertilizers  contain.  Investigation  and  ex- 
perience have  shown  that  in  most  instances  increased  production 
has  resulted  from  the  addition  to  the  soil  of  but  three  of  the 
essential  substances  found  in  plants;  namely:  nitrogen,  phos- 
phoric acid  and  potash.  It  has  been  shown  that  in  normal  soils 
there  are  probably  sufficient  quantities  of  all  the  other  elements 
which  the  plant  requires.  It  was  customary,  soon  after  the  time 
of  Liebig,  for  agricultural  investigators  to  add  all  the  elements 
essential  to  plant  growth,  but  practice  soon  showed  that  to  be 
unnecessary,  for  the  reason  stated  above.  Consequently  com- 
mercial fertilizers,  as  placed  on  the  market  today,  contain  only 
nitrogen,  phosphoric  acid  or  potash,  or  mixtures  of  these  ingre- 
dients and  these  are  the  only  elements  giving  the  fertilizer  com- 
mercial value. 

Commercial  fertilizers  are  made  from  a  few  basal  materials 
which  are  articles  of  commerce.  Some  of  these  materials  contain 
only  one  of  the  essential  ingredients  of  a  fertilizer,  while  others 
contain  two,  but  usually  one  is  in  such  excess  that  the  material 
is  used  chiefly  to  furnish  but  the  one  element. 

The  "complete  fertilizer"  consists  of  two  or  more  of  these 


Agricultural  Chemistry. 


basal  materials  mixed  together  to  give  the  desired  per  cent  of 
nitrogen,  phosphoric  acid  and  potash. 

Nitrogenous  fertilizers.     This  group   of  substances  may  be 
divided  into  two  classes:     (1)  Inorganic  or  mineral  substances; 


Complete 
Fertilizer 


Without 

Phosphoric 

Acid 


Without 
Potash 


Withoul 
Nitrogei 


Effect  of  fertilizer  constituents  upon  oats  grown  on  clay  soil.  Note 
scarcity  of  foliage  where  no  nitrogen  was  supplied  and  the 
yield  of  grain  where  phosphoric  acid  was  lacking. 

(2)  organic  substances  derived  from  animal  or  vegetable  rm 
rials.     The  inorganic  materials  most  commonly  used  are  sulphate 
of  ammonia,  nitrate  of  soda  and  nitrate  of  potash. 


Commercial  Fertilizers.  149 

Sulphate  of  ammonia.  This  material  is  from  the  gas  works 
and  is  obtained  as  a  by-product  in  the  manufacture  of  illumin- 
ating gas.  It  is  the  most  concentrated  nitrogenous  material  in 
the  market  and  contains  from  20  to  23  per  cent  of  nitrogen, 
equivalent  to  about  25  per  cent  of  ammonia.  It  is  very  soluble 
in  water,  does  not  readily  leach  out  of  the  soil,  and  undergoes 
nitrification  very  quickly,  being  converted  into  nitrates.  How- 
ever, some  plants  may  take  a  part  of  their  nitrogen  supply  di- 
rectly as  ammonium  salts,  when  so  applied.  The  sulphate  gives 
good  results  on  soils  containing  plenty  of  lime.  It  should  not 
be  used  on  soils  deficient  in  lime,  because  of  its  tendency  to  leave 
the  soil  acid. 

Nitrate  of  soda.  This  fertilizer  is  known  under  the  name  of 
"Chili  salt  petre"  and  occurs  in  deposits  of  considerable  extent 
in  Chili.  When  crude  it  is  called  " caliche"  and  contains  vary- 
ing amounts  of  impurities,  chiefly  common  salt.  It  is  freed  from 
these  impurities  by  solution  and  crystalization  and  when  put 
upon  the  market  contains  from  95  to  97  per  cent  of  nitrate  of 
soda,  This  final  product  contains  from  15  to  16  per  cent  of 
nitrogen.  Chili  supplies  over  a  million  tons  of  nitrate  a  year 
to  be  used  as  a  fertilizer.  This  substance  contains  its  nitrogen 
in  the  most  readily  assimilable  form,  and  in  the  form  into  which 
most  other  nitrogenous  bodies  must  be  converted  before  they  are 
taken  up  by  the  plant.  It  is  not  fixed  by  the  soil  and  unless 
growing  crops  are  at  hand  to  take  it  up,  it  will  be  leached  out  by 
rains.  Consequently  it  should  be  applied  as  a  top  dressing  and 
in  not  too  heavy  applications.  It  is  best  applied  early  in  the 
spring  soon  after  the  plants  have  started  their  growth  and  should 
be.  mixed  with  at  least  double  its  weight  of  soil  before  being  ap- 
plied, as  otherwise  harm  to  the  plants  may  result.  It  should  not 
be  applied  to  grain  crops  late  in  the  season. 

Nitrate  of  potash.  This  is  commonly  known  as  "salt  petre" 
and  is  one  of  the  most  concentrated  fertilizing  materials  we  have, 
since  it  contains  both  nitrogen  and  potash  in  available  forms. 
It  contains  about  13  per  cent  of  nitrogen  and  from  42  to  45  per 


150  Agricultural  Chemistry. 

cent  of  potash.  It  is  generally  too  .expensive  to  use  for  manurial 
purposes,  as  it  is  used  very  extensively  in  various  manufacturing 
processes. 

Calcium  nitrate.  This  product  is  manufactured  by  passing 
strong  electric  discharges  through  air.  By  this  means  oxides 
of  nitrogen  are  produced  by  the  union  of  oxygen  and  nitrogen. 
These  gases  are  absorbed  in  water  with  the  production  of  nitric 
acid.  This  acid  is  then  led  into  milk  of.  lime,  which  results  in 
the  formation  of  calcium  nitrate.  The  product  is  next  concen- 
trated until  it  solidifies  as  a  material  containing  about  13  per  cent 
of  nitrogen.  At  the  present  time  it  is  almost  entirely  produced 
in  Norway,  where  cheap  water  power  is  available,  and  in  cheap- 
ness compares  favorably  with  nitrate  of  soda.  As  a  fertilizer 
and  as  a  source  of  nitrogen  it  has  given  excellent  results. 

Calcium  cyanamide  is  a  comparatively  now  nitrogen-contain- 
ing fertilizer  and  is  produced  by  heating  calcium  carbide  in  a 
current  of  air  from  which  the  oxygen  has  been  removed.  When 
used  as  a  manure  it  has  in  many  cases  given  as  good  results  as 
the  same  amount  of  nitrogen  applied  as  nitrate  of  soda  or  am- 
monium sulphate.  Because  of  its  injurious  effect  on  germinat- 
ing seeds,  it  should  be  incorporated  with  the  soil  a  week  or  so 
before  any  seed  is  sown.  It  contains  about  20  per  cent  of  niti 
gen,  and  is  to-day  produced  in  limited  quantities  in  this  counti 

Organic  nitrogenous  materials.     In  order  to  bring  out  cleai 
the  relative  value  of  this  class  of  fertilizing  materials  they 
be  discussed  under  the  following  heads; ;  first,  those  materials 
which  the  nitrogen  becomes  readily  available  in  a  comparative 
short  time  by  decomposition  in  the  soil;  second,  those  materii 
which  undergo  fermentation  very  slowly  and  the  nitrogen 
which  only  becomes  available  after  a  long  time.     Readily  avi 
able  materials  include  such  products  as  dried  blood,  meat  sera] 
tankage,  dried  fish  or  fish  scrap,  cotton-seed  meal  and  cast 
pomace. 

Dried  blood.     This  material  is  obtained  by  drying  the  bl< 
from  shi lighter  houses.     Two  grades  are  found  on  the  market,  I 


Commercial  Fertilizers.  151 

known  as  red  and  black  blood.  The  red  variety  has  been  more 
carefully  dried,  while  the  black  blood  has  resulted  from  a  too 
rapid  drying.  The  red  blood  contains  from  13  to  14  per  cent 
of  nitrogen,  while  the  black  variety  is  less  constant  in  composi- 
tion and  contains  from  6  to  12  per  cent.  Dried  blood  ferments 
very  readily  in  the  soil  and  is  one  of  the  most  valuable  organic 
materials. 

Meat  scrap  or  meat  meal.  This  is  a  packing  house  product 
and  consists  of  various  parts  of  animal  bodies  that  have  been 
kept  separate  from  the  tankage.  It  is  rather  variable  in  com- 
position, containing  usually  from  10  to  12  ]5er  cent  of  nitrogen, 
with  a  small  amount  of  phosphoric  acid — about  3  per  cent.  It 
is  often  used  for  feeding  purposes,  as  well  as  for  fertilizer. 

Tankage.  This  is  a  general  mixture  of  the  refuse  material 
from  the  slaughter  houses.  It  has  usually  been  steam-cooked  in 
order  to  separate  the  fat  and  gelatine,  a  process  which  renders  it 
more  easily  fermentable  in  the  soil.  From  the  great  variations 
in  the  nature  of  the  materials  entering  into  its  make-up,  it  must 
of  necesssity  have  a  variable  composition.  It  contains  from  4 
to  9  per  cent  of  nitrogen  and  from  3  to  12  per  cent  of  phosphoric 
acid.  It  is  a  valuable  form  of  fertilizer  as  it  supplies  the  crop 
with  both  nitrogen  and  phosphoric  acid. 

Dried  fish  and  fish  scrap.  Most  of  the  fish  fertilizers  are 
made  from  menhaden,  a  fish  that  is  caught  in  large  numbers 
^along  the  Atlantic  coast.  The  fish  are  steamed  and  pressed  to 
extract  the  oil  and  the  remaining  '^pLQmace"  is  dried  and  ground. 
This  material  contains  from  8  to  11  per -cent  of  nitrogen  and 
3  to  5  per  cent  of  phosphoric  acid.  Some  of Itefish  fertilizers 
consist  of  the  residue  of  the  canning  factories,  but  these  are  not 
considered  so  valuable  as  those  derived  from  menhaden.  This 
material  readily  undergoes  nitrification  and  is  a  quick  acting 
fertilizer. 

Cotton-seed  meal.  This  is  obtained  by  removing  the  hulls 
and  oil  from  the  cotton  seed.  The  material  is  then  ground  and 
put  upon  th'  market.  It  contains  about  7  per  cent  of  nitrogen. 


152  Agricultural  Chemistry. 


per  cent  of  phosphoric  acid,  and  2  per  cent  of  potash.  It 
is  too  good  a  food  material  to  be  used  as  a  fertilizer,  as  it  is  con- 
sidered one  of  the  best  concentrated  feeds  on  the  market.  Its 
value  as  a  feed  is  becoming  more  and  more  recognized  and  it  is 
only  a  question  of  time  when,  like  linseed  meal,  it  will  no  longer 
be  available  as  a  fertilizer. 

Castor  pomace  is  a  by-product  in  the  manufacture  of  castor 
oil.  It  contains  5.5  per  cent  of  nitrogen,  about  2  per  cent  of 
phosphoric  acid  and  1  per  cent  of  potash. 

Slowly  available  materials.  Under  this  head  are  classed  such 
materials  as  leather  meal,  hoof  and  horn  meal,  and  hair  and  wool 
waste. 

Leather.  This  is  a  waste  product  from  various  factories  and 
is  sold  as  raw  leather,  steamed  leather  and  roasted  leather;  it 
contains  about  7  per  cent  of  nitrogen  and  in  the  soil  decays  very 
slowly.  When  finely  ground  it  is  sometimes  used  to  adulterate 
fertilizing  material. 

Hoof  and  horn  meal  is  a  by-product  resulting  from  the  mak- 
ing of  various  articles  from  hoofs  and  horns;  it  is  very  rich  in 
nitrogen,  carrying  about  14  per  cent,  but  decomposes  very  slowly 
in  the  soil. 

Hair.  This  is  another  product  from  slaughter  houses,  and 
when  dry  contains  from  9  to  14  per  cent  of  nitrogen.  It  is  very 
unavailable  and  should  not  be  used  in  its  natural  condition  for 
fertilizing  purposes. 

Wool  waste  is  the  waste  product  from  the  woolen  mills  and 
contains  from  5  to  6  per  cent  of  nitrogen  and  about  1  per  cent 
of  potash.  It  is  essentially  the  wool  fibres  which  have  become 
so  short  by  repeated  spinning,  weaving,  etc.,  that  they  will  no 
longer  hold  together.  It  is  a  low  grade  fertilizer. 

In  many  states  all  the  above  resistant  materials  are  prohibited 
from  sale  as  fertilizers.  This  appears  just,  since  in  their  original 
form  they  decay  so  very  slowly  as  to  make  them  of  little  value 
as  food  for  plants. 


Commerc'ial  Fertilizers.  153 

Experiments  indicate  that  if  nitrate  of  soda  is  rated  at  100 
per  cent,  the  availability  of  the  other  materials  will  be  as  follows : 

Per  cent 

Nitrate  of  soda 100 

Blood  and  cotton-seed  meal 70 

Fish (>5 

Bone  and  tankage 60 

Leather,  hair,  wool  waste,  etc 2 — 30 

This  suggests  that  for  those  crops  which  begin  their  growth 
early  in  the  spring,  the  best  results  will  follow  the  use  of  Chili 
salt-petre,  as  the  soil  is  likely  to  be  poor  in  nitrates  and  the 
process  of  nitrification  slow  at  that  time.  Other  crops,  as  corn, 
for  example,  which  make  their  growth  after  the  season  is  well 
advanced,  can  use  the  slower  acting  fertilizers ;  as  can  those  crops 
which  occupy  the  ground  permanently. 

In  ordinary  farming  it  is  seldom  profitable  to  purchase  nitro- 
genous fertilizers,  for  the  nitrogen  of  the  soil  can  be  maintained 
by  means  of  farm  manures  and  the  proper  use  of  leguminous 
crops  in  the  rotation.  In  intensive  farming,  as  market  garden- 
ing, it  will  be  found  necessary  to  make  liberal  use  of  nitrogenous 
fertilizers. 

Phosphatic  fertilizers.  Materials  from  which  phosphoric  acid 
is  derived  are  called  phosphates.  Commercial  sources  of  the 
phosphoric  acid  of  fertilizers  are:  (1)  phosphate  rock;  (2)  bones 
«nd  bone  preparations;  (3)  basic  slag;  (4)  guano. 

Phosphoric  acid  is  found  in  these  materials  in  combination 
with  lime,  iron  and  alumina.  In  combination  with  lime  it  forms 
three  different  compounds;  (1)  insoluble  phosphate  of  lime;  (2) 
soluble  phosphate  of  lime;  (3)  reverted  phosphate  of  lime. 

Insoluble  phosphate  of  lime  is  known  as  "tri-calcium  phos- 
phate," or  "bone  phosphate  of  lime"  and  is  composed  of  three 
parts  of  lime  in  combination  with  one  part,  of  phosphoric  acid. 
It  is  insoluble  in  water  and  not  readily  available  to  plants.  The 
principal  materials  found  on  the  market  containing  this  form 
of  phosphate  are : — South  Carolina  rock,  Florida  rock,  Tennessee 


1 :,  i  AfjriruUurn!  Chemistry. 

rock,  bones  and  tankage.  They  contain  from  25  to  30  per  cent 
of  phosphoric  acid.  Ground  into  a  fine  powder,  the  first  three 
are  sometimes  sold  under  the  name  of  "floats,"  which  on  account 
of  its  fineness  of  division  has  given  beneficial  results,  especially 
when  mix<-;l  with  stable  manure  or  applied  to  soils  rich  in  organic 
matter. 

Soluble  phosphate  of  lime.  This  substance  is  known  under 
several  names,  as  "one-lime  phosphate, "  "acid-phosphate,"  ''su- 
per-phosphate," "acidulated  rock,"  etc.  It  is  the  result  of 
treating  rock  phosphates  or  bones  with  sulphuric  acid.  By  this 
process  the  sulphuric  acid  combines  with  2  parts  of  the  lime, 
forming  sulphate  of  lime  or  gypsum.  This  leaves  a  compound 
which  contains  1  part  of  lime  and  2  parts  of  water,  in  combination 
with  the  1  part  of  phosphoric  acid  which  was  contained  in  the 
tri-calcium  phosphate.  This  substance  is  soluble  in  water,  read- 
ily diffuses  in  the  soil,  and  is  in  the  most  available  form  for  direct 
use  by  the  plant.  A  good  sample  of  acid-phosphate  contains 
about  .1 6  per  cent  of  phosphoric  acid.  While  easily  dissolved  by 
water,  it  is  not  leached  out,  as  several  constituents  of  the  soil  such 
as  humus,  lime,  iron  and  aluminum  compounds  have  the  power 
of  fixing  and  retaining  it  for  the  use  of  plants. 

Reverted  phosphate  of  lime.  In  making  super-phosphate  the 
whole  of  the  insoluble  phosphate  is  not  acted  upon.  The  tri- 
calcium  phosphate  which  remains  after  the  treatment  with  acid, 
when  left  in  contact  with  a  comparatively  large  amount  of  soluble 
phosphate,  causes  a  reversion  of  some  of  the  soluble  material  to 
what  is  called  ' '  reverted  "  or  "  gone  back ' '  phosphate.  It  is  also  » 
known  as  "di-calcium"  phosphate,  "citrate-soluble,"  and  "pre- 
cipitated phosphate."  In  composition,  this  material  falls  be- 
tween the  tri-calcium  and  mono-calcium  phosphates.  It  is  quite  i 
insoluble  in  pure  water,  but  can  be  dissolved  by  weak  acids,  and 
by  water  containing  carbonic  acid,  or  by  ammonium  .salts.  As 
the  soil  moisture  contains  salts  in  solution,  as  well  as  carbon  di- 
oxide, this  phosphate  is  readily  assimilated  by  plants  ..and  is  con- 
sidered an  available  form.  This  form  of  phosphate  is  considered 


Commercial  Fertilizers. 


155 


to  be  more  available  to  the  plant  than  the  insoluble  or  natural 
phosphate ;  hence,  the  soluble  and  reverted  phosphoric  acids  taken 
together  are  known  as  the  available  phosphoric  acid.  -7 

Phosphate  rock.  This  substance  has  already  been  mentioned 
under  insoluble  phosphate  of  lime.  Rock  phosphate  is  designated 
usually  by  the  locality  from  which  it  is  obtained,  as: — South 
Carolina  rock,  Florida  rock,  Tennessee  rock,  etc.  It  contains  2f> 
to  30  per  cent  of  phosphoric  acid  and  furnishes  the  chief  source 
of  the  supply  found  on  our  markets.  Apatite  is  a  purer  mineral 


Florida  rock-phosphate  mining. 

phosphate  and  it  found  in  considerable  quantities  in  Canada, 
Norway,  Sweden  and  Spain.  Mention  has  already  been  made  of 
the  finely  ground  rock  phosphate  known  as  "floats."  Recent 
investigations  indicate  that  when  this  material  is  added  to  farm 
manure  it  has  a  high  fertilizing  value ;  in  fact  the  increased  crop 
production  at  the  Ohio  Experiment  Station,  due  to  adding  ground 
rock  phosphate  to  stall  manure  was  nearly  as  large  as  that  ob- 
tained from  the  addition  of  super-phosphate.  It  would  seem 
from  these  experiments  that  the  comparatively  inexpensive  floats 
might,  partially  at  least,  replace  super-phosphate,  if  used  in  con- 


156  Agricultural  Chemistry. 

nection  with  manure  or  on  soils  rich  in  organic  matter.  The 
reason  usually  assigned  for  the  necessity  of  incorporating  this 
material  with  organic  matter,  is  that  the  latter  in  its  decay,  lib- 
erates acids,  which  attack  the  phosphate  and  render  it  more 
available. 

Bone  meal  or  ground  bone  is  a  product  of  the  packing  houses, 
glue  factories  and  soap  works,  the  raw  material  being  the  bones 
of  farm  animals.  These  are  either  ground  directly  (raw  bones) 
or  after  having  been  steamed  and  dried  (steamed  bones).  This 
latter  process  removes  nearly  all  the  fat,  tendons  and  the  nitro- 
genous tissue  adhering  to  the  bones.  The  steamed  bone  which 
comes  from  the  glue  or  soap  factories,  is,  as  a  result  of  the  process 
of  steaming,  poorer  in  nitrogen  and  richer  in  phosphoric  acid  than 
the  raw  bones.  Raw  bone  contains  about  2.5  per  cent  of  nitrogen 
and  25  per  cent  of  phosphoric  acid,  while  the  average  figures  for 
steamed  bone  are  0.5  per  cent  and  29  per  cent  of  nitrogen  and 
phosphoric  acid,  respectively.  The  effect  of  bone  meal  on  crops 
is  largely  dependent  on  its  degree  of  fineness,  since  it  will  be  de- 
composed more  quickly  in  the  soil  the  finer  it  is  ground.  Again, 
the  raw  bone  meal  decomposes  more  slowly,  due  to  the  presence 
of  fat  which  retards  such  processes ;  while  the  steamed  bones  not 
only  allow  a  much  more  perfect  pulverization,  but  also  a  more 
rapid  decomposition  in  the  soil,  and  consequently  are  considered 
of  somewhat  higher  availability.  Both  materials  contain  th^ 
phosphoric  acid  in  the  form  of  insoluble  phosphate  of  lime.' 

Bone  ash  is  incinerated  cattle  bones,  imported  from  South 
America;  the  nitrogenous  constituents  of  the  bones  have  been 
lost  in  the  process  of  burning.  It  consists  chiefly  of  the  insol- 
uble phosphate  of  lime  and  contains  from  30  to  35  per  cent  of 
phosphoric  acid.  Bone  black  or  animal  charcoal  is  a  refuse  prod- 
uct from  sugar  refineries  and  contains  about  33  per  cent  of  phos- 
phoric acid. 

Dissolved  bone  is  made  by  treating  raw  bone  with  sulphuric 
acid.  By  this  process  the  insoluble  phosphate  is  converted  into 
soluble  phosphate  and  the  organic  nitrogenous  material  into 


Commercial  Fertilizers.  157 

soluble  forms.  This  substance  contains  from  2  to  3  per  cent  of 
nitrogen  and  15  to  17  per  cent  of  available  phosphoric  acid.  It 
will  be  seen  that  in  respect  to  its  nitrogen  content  it  differs  ma- 
terially from  dissolved  rock  or  acid  phosphate,  which  does  not 
contain  this  element.  The  term  "dissolved  bone"  is  often  used 
in  speaking  of  "dissolved  rock,"  as  for  example,  "dissolved 
South  Carolina  bone."  This  use  of  the  term  is  incorrect,  as 
there  is  no  bone  in  South  Carolina  rock  phosphate. 

Basic  slag,  also  called  "Thomas  slag,"  or  "odorless  phos- 
phate," is  a  by-product  in  the  manufacture  of  iron  and  steel 
from  pig  iron  containing  phosphorus.  It  contains  from  15  to  20 
per  cent  of  phosphoric  acid  in  a  form  differing  slightly  from  the 
phosphates  already  discussed.  In  this  material  there  are  five 
parts  of  lime  combined  with  one  part  of  phosphoric  acid.  The 
material  is  insoluble  in  water,  but  readily  soluble  in  saline  solu- 
tions. From  the  results  of  numerous  experiments  it  has  been 
found  that  this  material  has  a  high  degree  of  availability,  about 
equal  to  one-half  that  of  a  soluble  phosphate.  Its  value  as  a 
fertilizer  partly  depends  upon  its  fineness  of  division.  The  finer 
it  is  ground  the  more  quickly  it  will  become  available.  The  fact 
that  it  contains  a  high  lime  content  has  made  it  particularly  de- 
sirable for  acid  soils,  on  which  it  has  given  excellent  results. 

Guano.  Many  mixed  fertilizers  and  fertilizing  materials  are 
incorrectly  spofcen  of  as  "  guano. ' '  The  term^hpuld  be  applied  to 
the  natural  product  only,  which  consists  of  the  excrement  and 
remains  of  sea  fowls,  and  which  have  accumulated  in  certain  re- 
gions along  the  coast  of  South  America  and  on  some  of  the  is- 
lands in  the  Carribean  sea.  There  are  two  kinds,  dependent  upon 
the  conditions  under  which  they  were  formed.  When  the  forma- 
tion took  place  in  a  dry  warm  region,  the  excrement  dried  quick- 
ly and  remained  practically  unchanged.  This  will  contain  all 
the  nitrogen,  phosphoric  acid  and  potash  originally  in  the 
manure.  Some  of  the  early  guanos  contained  as  high  as  20  per 
cent  of  nitrogen,  but  those  now  on  the  market  are  of  poorer 


158  Agricultural  Chemistry. 

quality  and  contain  from  2  to  9  per  cent  of  nitrogen,  9  to  19 
per  cent  of  phosphoric  acid  and  2  to  4  per  cent  of  potash.  "Where 
the  formation  has  taken  place  in  a  damp  climate,  then  ferment- 
ation occurred,  resulting  in  a  loss  of  nearly  all  of  the  organic 
nitrogen.  If  much  rain  fell,  there  was  also  a  loss  of  nearly  all 
of  the  soluble  potash  salts  and  soluble  phosphates.  This  has  pro- 
duced a  product  containing  15  to  30  per  cent  of  phosphoric  acid 
in  the  form  of  insoluble  phosphates  of  lime,  iron  and  aluminum. 
This  material  is  generally  converted  into  a  soluble  phosphate  by 
treatment  with  sulphuric  acid,  before  reaching  the  market. 

Potash  fertilizers.  This  class  of  materials  is  generally  con- 
sidered of  relatively  less  importance  as  fertilizers  than  either 
the  nitrogenous  or  phosphatic  fertilizers.  This  is  true  because 
potash  compounds  are  usually  more  abundant  in  the  soil  than 
either  nitrogen  or  phosphoric  acid,  and  while  most  crops  remove 
larger  quantities  of  potash  than  of  phosphoric  acid,  the -former 
is  more  likely  to  be  returned  to  the  soil.  It  has  already  been 
stated  that  potash  is  most  abundant  in  the  stems  and  leaves  of 
plants,  and  as  they  are  the  materials  generally  returned  to  the 
land  in  the  form  of  manure,  the  drain  from  the  soil  of  this  con- 
stituent is  therefore  much  less  than  in  the  case  of  the  nitrogen 
and  phosphoric  acid.  Of  course,  when  the  whole  of  the  crop  is 
removed  from  the  soil  the  loss  of  this  constituent  may  be  very 
great.  "While  these  are  important  facts,  it  must  not  be  assumed 
that  the  addition  of  potash  fertilizers  is  unnecessary.  It  is  a 
very  necessary  constituent  of  fertilizers,  being  absolutely  essen- 
tial for  those  intended  for  light,  sandy  soils,  and  for  peaty- 
meadow  lands,  as  well  as  for  certain  potash-consuming  crops,  as 
potatoes,  tobacco  and  roots.  They  are  also  of  especial  value  for 
clover,  grass,  corn  and  fruits;  they  should  be  applied  in  the 
fall  on  heavy  clay  soils  and  in  the  early  spring  on  sandy  soil. 
The  former  soils  generally  do  not  need  applications  of  potash 
salts  as  much  as  sandy  soils,  being  naturally  rich  in  this  fer- 
tilizer ingredient. 


Commercial  Fertilizers.  159 

The  commercial  materials  on  the  market  are  muriate  of  potash, 
•sulphate  of  potash,  sulphate  of  potash  and  magnesia,  kainit,  to- 
bacco stems  and  wood  ashes. 

Muriate  of  potash  is  manufactured  by  concentration  from  the 
crude  minerals  obtained  from  the  Stassfurth  mines  of  Germany. 
These  mines  of  Stassfurth  are  immense  saline  deposits,  formed 
by  evaporation  of  large  inland  seas,  cut  off  from  the  ocean  by 
geological  changes.  These  deposits  are  the  main  source  of  all 
commercial  potash  fertilizers.  The  muriate  contains  about  50 
per  cent  of  potash,  all  of  which  is  combined  with  chlorine.  At 
the  present  price  per  ton  it  supplies  potash  at  a  cheaper  price 
per  pound  than  any  of  the  other  materials.  It  can  be  used  on 
all  soils  and  all  crops  except  a  few,  such  as  tobacco,  potatoes  and 
sugar  beets,  which  appear  to  be  injured  in  quality  by  the  chlorine 
present. 

Sulphate  of  potash.  This  is  another  concentrated  product  of 
the  Stassfurth  industry.  "What  is  known  as  "high  grade  sul- 
phate" contains  about  50  per  cent  of  potash  in  the  form  of 
•sulphate.  A  low  grade  is  also  made,  which  contains  from  30 
to  35  per  cent  of  potash.  The  sulphate  of  potash  is  of  special 
value  for  those  crops  injured  by  chlorides,  as  mentioned  above. 

Sulphate  of  potash  and  magnesia.  This  is  sometimes  called 
^'double  manure  salt,"  It  is  obtained  from  the  Stassfurth 
mines,  and  contains  25  to  28  per  cent  of  potash.  It  is  a  mixture 
of  magnesium  sulphate  and  potassium  sulphate.  Unless  the  cost 
per  pound  of  actual  potash  in  this  material  is  less  than  in  other 
forms,  it  has  no  special  quality  to  recommend  it. 

Kainit.  This  is  the  most  common  product  of  the  Stassfurth 
mines  and  is  a  mixture  of  various  salts.  It  contains  from  12  to 
14  per  cent  of  potash,  chiefly  in  the  form  of  sulphate.  It  also 
contains  a  considerable  quantity  of  common  salt,  some  chloride 
and  sulphate  of  magnesium,  a  small  quantity  of  gypsum  and  a 
small  amount  of  potassium  chloride.  It  is  a  low  grade  potash 
salt  and  while  it  is  cheaper  per  ton,  the  actual  potash  costs  more 
in  kainit  than  in  the  muriate  or  high  grade  sulphate.  For  this 


Agricultural  Chemistry. 


reason  it  is  not  desirable  to  purchase  it  for  making  home  mix- 
tures. As  it  contains  chlorides  it  should  not  be  used  as  a  fer- 
tilizing material  for  tobacco,  potatoes,  or  sugar  beets.  When 
used  it  should  be  carefully  applied  to  the  soil  so  that  it  will  not 
come  in  contact  with  the  seed,  as  it  may  seriously  interfere  with 
germination. 

Tobacco  stems.     This  is  a  by-product  from  tobacco  factories. 
It  readily  undergoes  decomposition  in  the  soil,  its  potash  thus  be- 


Potash  mines  at  Stassfurth,  Germany.  Mining  potash  for  fertilizers. 
coming  available.  It  contains  from  2  to  2V2  per  cent  of  nitrogen, 
from  6  to  8  per  cent  of  potash  and  from  3  to  5  per  cent  of  pho^- 
phoric  acid.  In  states  where  it  can  be  secured  at  a  compara- 
tively low  price,  it  can  be  used  very  profitably  in  making  fer- 
tilizer mixtures. 

Wood  ashes.  For  many  years  they  were  the  sole  source  of 
potash  for  fertilizing  purposes,  but  since  the  introduction  of 
the  German  potash  salts,  there  is  less  of  this  material  found  on 
the  market.  They  are  valuable  when  unleached,  containing  in 
this  condition  from  2  to  8  per  cent  of  potash.  They  are  largely 


Commercial  Fertilizers.  161 

composed  of  carbonates  of  lime,  magnesia  and  potash,  with  a 
small  quantity  of  phosphates  (%  per  cent).  The  ashes  from 
soft  woods  contain  less  potash  than  those  from  hard  woods.  Coal 
ashes  have  practically  no  value  for  fertilizing  purposes.  Wood 
ashes  have  a  beneficial  action  on  the  mechanical  condition  of 
light  soils,  mainly  because  of  the  large  amount  of  lime  they  con- 
tain. This  binds  the  soil  particles  together,  thus  increasing  their 
capillary  action  and  improving  their  tilth.  On  clay  soils  there 
is  a  tendency  for  wood  ashes  to  cause  "puddling."  This  is 
avoided  by  applying  an  equal  quantity  of  land  plaster  with  the 
ashes. 

All  the  materials  mentioned  with  the  exception  of  tobacco 
stems  are  soluble  in  water,  so  there  is  no  such  marked  difference 
in  availability  as  was  noted  in  the  case  of  nitrogenous  and  phos- 
phatic  fertilizers. 

Indirect  fertilizers.  There  are  a  number  of  substances  which 
are  beneficial  to  the  land  under  some  conditions,  although  they 
add  neither  humus  nor  important  quantities  of  plant  food. 
Among  such  materials  are  lime,  gypsum  and  common  salt. 

Lime.  There  are  very  few  if  any  soils,  which  do  not  contain 
sufficient  lime  to  supply  the  plant.  The  chief  value  of  lime  ap- 
plications must  be  as  an  indirect  fertilizer.  Its  action  is  three- 
fold:— Mechanical,  chemical  and  biological.  Its  mechanical  ef- 
fect on  heavy  soils  is  to  make  them  less_adJ3£siYfi_and  more  friable 
and  easier  to  work  when  dry.  On  light  porous  soils  its  effect  is 
exactly  the  reverse.  It^binda  the  particles  together,  increases 
the  cohesive  power  and  improves  capillarity.  Chemically,  its 
action  is  important.  It  acts  on  insoluble  potash  compounds, 
liberating  potash.  It  aids  in  the  decomposition  of  organic  mat- 
ter. It  corrects  acidity  by  combining  with  the  acids  present. 
Its  biological  action  is  dependent  upon  the  chemical  reactions 
it  induces.  Its  presence  is  a  necessary  condition  to  nitrification, 
a  biological  process.  It  combines  with  the  nitric  acid  .formed, 
producing  nitrates.  By  maintaining  the  soil  neutral,  or  slightly 
alkaline,  it  creates  a  proper  medium  for  the  growth  and  develop- 


362  Agricultural  Chemistry. 

ment  of  many  forms  of  micro-organisms,  which  are  so  necessary 
to  the  formation  of  available  plant  food. 

Lime  for  agricultural  purposes  is  put  upon  the  market  in 
several  different  forms: — as  caustic  lime;  as  hydrate  of  lime  or 
water-slaked  lime;  as  air  slaked  lime  or  carbonate  of  lime;  as 
ground  limestone  rock  and  as  ground  oyster  or  clam  shells.  The 
caustic  or  quick  lime  is  the  most  concentrated  form  and  the  most 
active.  It  is  made  up  of  the  two  elements,  calcium  and  oxygen. 
When  they  unite  we  have  quick  lime,  or  calcium  oxide,  and  this 
material  when  united  with  carbon  dioxide  forms  calcium  car- 
bonate, the  chief  constituent  of  limestone  and  oyster  and  clam 
shells.  When  limestone  is  burned  quick-lime  or  calcium  oxide 
is  left  behind.  One  hundred  pounds  of  pure  calcium  carbonate 
will  yield  on  burning  56  pounds  of  calcium  oxide,  and  44  pounds 
of  carbon  dioxide  will  be  driven  off.  From  the  quick  lime,  the 
slaked  lime  is  obtained  by  addition  of  water  out  of  contact  with 
the  air.  Fifty-six  pounds  of  caustic  become  76  pounds  of  slaked 
lime.  When  contact  of  air  is  allowed  the  56  pounds  of  caustic 
become  100  pounds  of  air  slaked  lime  by  again  combining  with 
the  carbon  dioxide  of  the  air.  Thus  it  will  be  seen  that  in 
purchasing  lime  it  will  be  more  economical  to  buy  the  caustic  or 
quick  lime.  However,  because  of  its  quick  action,  care  must  be 
exercised  in  its  use.  Finely  ground  limestone  is  coming  into 
high  favor  and  where  it  can  be  obtained  at  a  sufficiently  low  cost 
is  undoubtedly  the  safest  form  to  use,  especially  by  the  inex- 
perienced. Lime  should  be  applied  to  the  surface  and  if  pos- 
sible thoroughly  incorporate  with  the  few  upper  inches  of  the 
soil.  The  clovers  and  other  leguminous  plants  require  more 
lime  than  do  the  cereals  and  are  much  more  sensitive  to  acidity 
of  the  soil.  A  good  stand  of  clover,  therefore,  is  an  indication 
that  the  soil  contains  sufficient  lime. 

Gypsum  or  land  plaster  is  a  sulphate  of  lime  and  has  given 
excellent  results  with  clover  and  other  leguminous  plants.  It 
is  now  generally  believed  that  its  beneficial  action  is  due  to  the 
fact  that  the  plaster  sets  free  the  unavailable  potash  of  the  soi 


Commercial  Fertilizers.  163 

It  is  of  value  to  those  crops  that  are  benefited  by  the  use  of 
potash.  For  that  reason  it  gives  best  returns  when  used  on  soils 
rich  in  potential  potash,  as  the  clays,  with  practically  no  bene- 
ficial results  when  applied  to  sandy  soils.  Its  use  as  a  source  of 
sulphur  must  not  be  overlooked,  as  it  is  possible  that  the  bene- 
ficial results  obtained  in  many  cases  by  its  application  will  hava 
to  be  traced  back  to  the  additional  supply  of  this  element. 

Salt  has  sometimes  been  used  as  a  manure.  It  is  certain  that 
in  special  cases  it  has  given  beneficial  results,  but  in  other  in- 
stances injury  has  resulted.  It  is  well  known'  that  salt  checks 
fermentations  of  all  kinds  so  that  it  probably  influences  the  rate 
of  nitrification  going  on  in  the  soil.  It  is  said  that  ^adding  salt 
will  make  the  straw  of  wheat  stiffer,  but  this  effect  is/probably 
due  to  the  fact  that  salt  depresses  the  plant's  growth,  making 
the  straw  shorter  and  consequently  stiffer,  due  to  reduced  length. 

Mixed  fertilizers.  The  tendency  of  the  fertilizer  trade  in  this 
country  has  been  toward  the  manufacture  and  sale  of  mixed 
fertilizers.  They  have  been  sold  in  the  form  known  as  complete 
fertilizers,  which  consist  of  a  mixture  of  two  or  more  of  the 
basal  materials  heretofore  described.  Where  the  basal  material 
alone  is  richer  in  the  essential  ingredient  than  is  desired  by  the 
manufacturer,  sufficient  gypsum,  dry  earth,  peat  or  other  inert 
matter  is  added  to  bring  the  percentage  of  these  ingredients  down 
to  the  desired  point.  Mixed  fertilizers  are  indiscriminately 
recommended  for  general  use  and  all  sorts  of  startling  claims  are 
made  for  them  by  the  manufacturers.  They  are  offered  as  uni- 
versal fertilizers,  irrespective  of  the  well  known  fact  that  soils 
differ  widely  in  their  characteristics  and  that  the  crops  vary  in 
their  food  requirements.  So-called  special  fertilizers,  designed 
for  special  crops  and  supposed  to  be  adapted  to  their  particular 
needs,  are  common  on  the  market.  Some  manufacturers  offer  a 
corn  special,  a  potato  special,  a  tobacco  special,  etc.  Unfortu- 
nately their  chief  claim  lies  in  their  attractive  names.  The 
science  of  plant  nutrition  has  not  advanced  to  that  stage  where 
one  can  define  what  the  minimum  of  essential  elements  necessary 


Agricultural  Chemistry. 


for  the  maximum  growth  of  the  plant  should  be.  And  even  if 
we  had  such  information,  the  makers  of  fertilizer  mixtures  en- 
tirely disregard  the  quantities  of  plant  food  already  existing  in 
the  soil  to  be  treated.  When  the  farmer  studies  the  apparent 
needs  of  his  fields  and  understands  the  subject  of  fertilization  of 
^rops,  he  will  prefer  to  buy  the  basal  fertilizing  materials  of  defi- 
nite, known  composition  and  make  the  proportion  best  adapted 
to  his  needs,  rather  than  buy  mixed  fertilizers. 

High  and  low  grade  fertilizers.  As  the  basal  materials  used 
in  compounding  fertilizing  mixtures  differ  greatly  in  the  amounts 
of  plant  food  they  contain,  it  will  be  seen  that  products  made  by 
mixing  these  materials  will  contain  very  different  percentages  of 
nitrogen,  phosphoric  acid  and  potash.  If,  for  example,  dried 
blood,  bone  meal  and  muriate  of  potash  were  used,  the  fertilizer 
would  have  a  high  content  of  plant  food,  while  if  low  grade  tank- 
age, wood  ashes,  or  kainit  were  employed,  the  product  would 
have  a  low  percentage.  The  first  example  illustrates  a  high 
grade  product,  while  the  second  would  be  considered  as  low 
grade. 

As  the  low  grade  material  can  be  sold  at  a  comparatively  low 
price,  these  materials  find  a  ready  market,  although  the  plant 
food  in  the  cheap  fertilizer  actually  costs  more  per  pound.  This 
fact  is  clearly  brought  out  in  the  following  table  taken  from  a 
recent  bulletin  of  the  New  York  Experiment  Station.  (Geneva). 
Average  Cost  of  One  Pound  of  Plant  Food  to  Consumers. 


Nitrogen 

Phosphoric  Acid 

Potash 

Low  grade  complete 
fertilizer  

Ctfl. 

•v,  :; 

Cis. 
8  0 

Cts. 

(i   S 

Medium  grade   com- 
plete fertilizer 

23  9 

7  0 

,  ;    i| 

High  grade  complete 
fertilizer  .  . 

1(<  c> 

,;    () 

*>  0 

Dried  blood  

18.5 

Nitrate  of  poda  

115   !l 

Acid   phosphate  . 

r>  i 

Muriate  of  potash  

]..; 

Commercial  Fertilizers.  165 

It  will  be  seen  that  the  price  per  pound  of  plant  food  is  very 
ijmuch  less  in  high  grade  goods  than  in  low  grade  goods,  and 
!  further,  that  the  essential  elements  can  be  purchased  separately 
ilinore  cheaply  than  in  any  mixed  fertilizer. 

Home  mixing.  The  above  facts  emphasize  the  wisdom  of  the 
'purchase  of  basal  materials  and  home  mixing.  The  difference  in 
cost  of  complete  fertilizers  and  the  basal  materials  per  pound 
•of  plant  food  is  to  be  partly  attributed  to  the  expense  of  bagging 
and  mixing.  This,  Voorhees  has  shown  to  amount  to  about  $8.50 
per  ton.  That  this  practice  of  home  mixing  is  entirely  satisfac- 
tory has  been  abundantly  proven  by  the  Eastern  Experiment 
iStations.  It  allows  the  uniting  of  the  different  elements  in  the 
proportions  which  have  been  found  to  meet  best  the  requirements 
:>f  the  crop  and  the  soil  on  which  the  crop  is  to  be  raised.  By 
buying  the  basal  materials  separately  it  is  possible  to  apply  the 
different  elements  at  different  times.  This  point  may  be  of 
sjreat  advantage  in  feeding  a  crop,  especially  one  needing  large 
'quantities  of  nitrogen. 

The  conditions  and  materials  necessary  to  do  the  mixing  are 
a  good,  tight  barn-floor,  or  a  dry,  smooth  earth-floor,  platform 
scales,  rake,  hoe,  shovel  and  screen. 

Selection  of  commercial  fertilizers.     It  is  impossible  to  give 
definite  directions  as  to  the  kinds  and  quantities  of  fertilizers 
*  required  for  different  crops,  because  soils  differ  greatly  in  their 
;  Itotal  content  of  plant  food,  and  we  have  no  direct  and  safe  meth- 
i  id  by  which  the  amounts  of  available  plant  food  can  be  accur- 
;  itely  determined.     By  noting  carefully  the  growing  crops,  we 
nay  get  in  a  general  way,  some  valuable  suggestions  as  to  which 
)f  the  constituents  is  probably  lacking  in  a  soil.     For  instance, 
the  crop  has  a  deep  green  color,  with  well  -developed  leaf 
stalk  and  luxuriant  growth,  it  may  be  assumed  that  the  soil 
ts  not  deficient  in  nitrogen  and  potash!     A  rank  and  excessive 
growth  of  leaf  and  stem,  with  imperfect  bud  and  flower  develop- 
ment indicate  excessive  nitrogen  for  the  potash  and  phosphoric 


j  ( ;  ( ;  A  gricultura I  Che mistry. 

acid  present.  When  grain  crops  tend  to  mature  early,  with  well 
defined,  well  developed,  plump  and  heavy  kernels,  there  will  be 
little  doubt  that  the  soil  contains  a  good  supply  of  available 
phosphoric  acid.  Potash  fertilizers  are,  generally  speaking,  of 
.special  lieiidit  in  the  case  of  leafy  plants  like  tobacco,  cabbage. 
beets,  clover  and  potatoes.  While  some  help  may  be  had  from  the 
above  suggestions,  nevertheless  definite  methods  of  procedure 
have  been  proposed  by  several  investigators,  and  will  be  dis- 
cussed briefly. 

Ville  system.     ';The  system  which  has  perhaps  received  the 
most  attention,  doubtless  largely  because  one  of  the  first  pre- 
sented, and  in  a  very  attractive  manner,  is  the  one  advocated  by 
the  celebrated  French  scientist,  George  Ville.    This  system,  while 
not  to  be  depended  upon  absolutely,  suggests  lines  of  practice 
which,  under  proper  restrictions,  may  be  of  very  great  service. 
In  brief,  this  method  assumes  that  plants  may  be,  so  far  as  their 
fertilization   is   concerned,   divided  into  three   distinct  groups. 
One  group  is  specifically  benefited  by  nitrogenous  fertilization, 
the  second  by  phosphatic,  and  the  third- by  potassic.     That  is, 
in  each  class  or  group,  one  element  more  than  any  other  rules 
or  dominates  the  growth  of  that  group,  and  hence  each  particular 
element  should  be  applied  in  excess  to  the  class  of  plants  for 
vvhich  it  is  a  dominant  ^agrediejat^In  this  system  it  is  asserted 
that  nitrogen  is  the  dominant  ingredient^JIpjp  wheat,  rye, 
barley,  meadow  grass  and  beet  crops.     Phosphoric  acid  is 
dominant  fertilizer  ingredient  for  turnips,  Swedes,  Indian  coi 
(maize),  sorghum,  and  sugar  cane;  and  potash  is  the  domin* 
or  ruling  element  for  peas,  beans,  clover,  vetches,  flax,  and  pol 
toes.     It  must  not  be  understood  that  this  system  advocates  onl] 
single  elements,  for  the  others  are  quite  as  important  up  to  i 
certain  point,  beyond  which  they  do  not  exercise  a  controlling 
influence  in  the  manures  for  the  crops  of  the  three  classes.     This 
special  or  dominating  element  is  used  in  greater  proportion  tl 
the  others,  and  if  soils  are  in  a  high  state  of  cultivation,  or  hi 


Commercial  Fertilizers.  167 

been  manured  with  natural  products,  as  stable  manure,  they 
may  be  used  singly  to  force  a  maximum  growth  of  the  crop. 
Thus,  a  specific  fertilization  is  arranged  for  the  various  rotations, 
the  crop  receiving  that  which  is  the  most  useful.  There  is  no 
doubt  that  there  is  a  good  scientific  basis  for  this  system,  and  that 
it  will  work  well,  particularly  where  there  is  a  reasonable  abund- 
ance of  all  the  plant  food  constituents,  and  where  the  mechanical 
and  physical  qualities  of  .the  soil  are  good,  though  its  best  use  is 
in  *  intensive'  systems  of  practice.  It  cannot  be  depended  upon 
to  give  good  results  where  the  land  is  naturally  poor,  or  run 
down,  and  where  the  physical  character  also  needs  improve- 
ment." 

Wagner  system.  "Another  system  which  has  been  urged, 
notably  by  the  German  scientist,  Wagner,  is  based  upon  the  fact 
that  the  mineral  constituents,  phosphoric  acid  and  potash,  form 
fixed  compounds  in  the  soil  and  are,  therefore,  not  likely  to  be 
leached  out,  provided  the  land  is  continuously  cropped.  They 
remain  in  the  soil  until  used  by  growing  plants,  while  the  nitro- 
gen, on  the  other  hand,  since  it  forms  no  fixed  compounds  and 
is  perfectly  soluble  when  in  a  form  useful  to  plants,  is  liable  to 
loss  from  leaching.  Furthermore,  the  mineral  elements  are  rel- 
atively cheap,  while  the  nitrogen  is  relatively  expensive,  and  the 
economical  use  of  this  expensive  element,  nitrogen,  is  dependent 
to  a  large  degree  upon  the  abundance  of  the  mineral  elements 
in  the  soil.  It  is,  therefore,  advocated  that  for  all  crops  and  for 
all  soils  that  are  in  a  good  state  of  cultivation,  a  reasonable  excess 
of  phosphoric  acid  and  potash  shall  be  applied,  sufficient  to  more 
than  satisfy  the  maximum  needs  of  any  crop,  and  that  the  nit- 
rogen be  applied  in  active  forms,  as  nitrate  or  ammonia,  and  in 
such  quantities  and  at  such  times  as  will  insure  the  minimum  loss 
of  the  element  and  the  maximum  development  of  the  plant.  The 
supply  of  the  mineral  elements  may  be  drawn  from  the  cheaper 
materials,  as  ground  bone,  tankage,  ground  phosphates  and  iron 
phosphates,  as  their  tendency  is  to  improve  in  character;  potash 


108  Agricultural  Chemistry. 

may  come  from  the  crude  salts.  Nitrogen  should  be  applied  as 
nitrate  of  soda,  because  in  this  form  it  is  immediately  useful, 
and  thus  may  be  applied  in  fractional  amounts,  and  at  such  times 
as  to  best  meet  the  needs  of  the  plant  at  its  different  stages  of 
growth,  with  a  reasonable  certainty  of  a  maximum  use  by  the 
plant.  Thus  no  unknown  conditions  of  availability  are  involved, 
and  when  the  nitrogen  is  so  applied,  the  danger  of  loss  by  leach- 
ing, which  would  exist  if  it  were  all  applied  at  one  time,  is  ob- 
viated."—  (Voorhees.) 

System  based  on  the  analysis  of  the  plant.  ' '  Still  another  sys- 
tem is  based  on  the  food  requirements  of  the  plant  as  shown  by 
the  analysis  of  the  plant  itself.  The  amount  of  plant  food  re- 
moved from  each  acre  of  ground  is  calculated  from  the  analysis 
of  the  plant  and  a  corresponding  amount  is  returned  to  the  soil. 
Different  formulas  are,  therefore,  recommended  for  each  crop, 
and  in  these  the  nitrogen,  phosphoric  acid  and  potash  are  com- 
bined in  the  same  proportions  in  which  they  are  found  in  the 
plant.  Experience  shows  that  it  is  necessary  to  add  amounts  of 
these  fertilizers  to  the  soil  that  will  supply  more  plant  food  than  "k 
is  removed  by  the  crop  if  the  maximum  results  are  desired.  This 
system  may  result  in  a  large  yield,  but  cannot  be  considered  an 
economical  method  of  feeding  the  plant,  as  one  or  more  of  the 
elements  is  likely  to  be  applied  in  excess  of  the  requirements  of 
the  crop.  It  does  not  take  into  consideration,  for  instance,  the 
fact  that  a  plant  which  contains  a  large  amount  of  one  element 
of  plant  food  may  possess  unusually  great  -power  of  procuring 
that  element  from  the  soil.  The  principle  underlying  this  sys- 
tem, of  course,  is  the  idea  that  to  maintain  the  fertility  of  the 
soil  unimpaired  an  amount  of  plant  food  equivalent  to  that  re- 
moved by  the  crop  must  be  returned  to  the  land.  To  this  extent 
the  system  is  similar  to  the  use  of  barnyard  manure,  but  is  not 
so  effective." 

Money  crop  system.     "  Another  system  used  in  ordinary  or 
extensive  farming  is  to  apply  all  the  fertilizer  to  the  money  ci 


Commercial  Fertilizers.  169 

of  the  rotation.  This  method  is  used  especially  where  only  one 
crop  in  a  rotation  is  sold,  the  others  being  fed  on  the  farm.  A 
liberal  supply  of  food  is  used  to  give  the  maximum  yield  which 
the  climate  and  season  will  permit.  The  amount  of  food  applied 
is  in  excess  of  the  requirements  of  the  crop  and  the  residue  is 
depended  upon  to  help  nourish  the  succeeding  crops,  or  at  least 
the  one  immediately  succeeding  the  money  crop.  This  system 
has  some  valuable  features  and  is  probably  the  one  most  in  use 
in  this  country  at  the  present  time. 

"Too  frequently  fertilizers  are  used  by  what  certain  writers 
have  called  the  'hit  or  miss'  system.  No  special  thought  is  given 
to  the  requirements  of  the  crop  or  the  composition  of  the  fer- 
tilizer, but  if  a  farmer  feels  that  he  can  afford  it  and  the  agent 
is  a  glib  talker,  the  sale  is  made.  If  the  buyer  happens  to  'hit' 
the  food  requirements  of  his  crop  a  profit  is  secured  and  he  is 
correspondingly  happy,  while  if  he  makes  a  'miss'  he  feels  as- 
sured that  there  is  no  value  in  commercial  fertilizers." — Viv- 
ian.) 

Field  experiments  necessary.  These  systems  described  have 
their  good  features,  but  they  do  not  take  into  account  the'  import- 
ant fact  that  soils  differ  greatly  in  the  amount  and  availability  of 
the  plant  food  they  already  contain.  In  order  to  determine  with 
any  degree  of  certainty  what  particular  constituents  are  needed 
the  farmer  must  conduct  some  experiments  for  himself.  This 
can  be  done  by  carefully  marking  off  certain  portions  of  the 
field,  of  definite  size  and  uniform  soil,  and  using  on  them  differ- 
ent fertilizing  materials.  Plots  one  rod  wide  and  8  rods  long, 
and  containing  1/20  of  an  acre,  are  of  convenient  size.  The  dia- 
gram on  page  170,  taken  from  Vivian,  shows  the  arrangement 
and  kinds  and  quantity  of  materials  to  be  used  on  each  plot. 

Careful  notes  should  be  made  during  the  growing  period  and 
at  the  end  of  the  growing  season  and  when  the  crop  is  harvested 
comparison  made  as  to  the  yields  by  weight  obtained.  In  this 
way  definite  information  will  be  secured  as  to  whether  the  soil 


170  Agricultural  Chemistry. 

is  lacking  in  one  or  two,  or  all  three  of  the  constituents  of  plant 
food  in  available  form.  In  carrying  out  field  tests  such  as  these 
it  should  be  borne  in  mind  that  the  results  of  one  year's  work 
are  not  perfectly  reliable,  since  prevailing  weather  conditions, 
as  well  as  other  factors,  may  produce  very  different  results.  It 
will  be  well  to  continue  tne  work  for  several  years  in  order  to 
eliminate  any  differences  due  to  differences  of  season. 


No    Fertilizer 


15  Ibs.  Nitrate  of  Soda 
15  Ibs.  Sulphate  of  Potash 
30  Ibs.  Acid  Phosphate 


30  Ibs.  Acid  Phosphate 
15  Ibs.  Sulphate  of  Potash 


No   Fertilizer 


15  Ibs.  Nitrate  of  Soda 
15  Ibs.  Sulphate  of  Potash 


15  Ibs.  Nitrate  of  Soda 
30  Ibs.  Acid  Phosphate 


No   Fertilirer 


It  must  also  be  remembered  that  the  requirements  for  different 
crops  will  vary.  By  carrying  the  plots  through  several  seasons 
and  using  the  rotation  common  for  that  particular  farm,  the 
special  crop  needs  can  also  be  ascertained. 

Amount  of  fertilizers  to  be  applied.  No  definite  rules  can  be 
given  as  to  the  quantities  of  commercial  fertilizers  to  be  applied, 
for  the  amount  necessary  to  produce  large  crops  will  vary  with 
the  character  and  state  of  fertility  of  the  soil,  the  kind  of  crop 


Commercial  Fertilizers.  171 

to  be  grown,  the  time  and  manner  of  application  and  many  other 
factors.  Five  hundred  pounds  per  acre  may  be  considered  a 
heavy  application  for  ordinary  farm  crops ;  applications  of  more 
than  that  amount  will  only  give  economical  returns  in  the  case 
of  special  crops  grown  under  an  intensive  system  of  farming. 
Heavy  applications  at  long  intervals  are  not  as  productive  of 
good  results  as  light  applications  more  frequently.  It  is  better 
not  to  make  applications  of  over  200  pounds  per  acre  of  any  one 
basal  material  and  to  vary  the  amount  from  year  to  year  until 
experience  has  shown  that  economical  returns  can  be  expected  by 
heavier  applications.  Lime  may  be  applied  at  the  rate  of  1000 
pounds  per  acre  on  light  soils  and  double  that  amount  on  heavy 
soils.  This  application  once  in  5  or  6  years  is  usually  sufficient. 
Fertilizer  laws  and  guarantees.  To  protect  the  farmer  against 
the  sale  of  fraudulent  and  spurious  goods,  the  manufacturers  are 
compelled  by  law  in  most  states,  to  give  the  actual  amounts  of  the 
different  constituents  contained  in  their  products.  Usually 
they  are  compelled  by  law  to  state  on  each  bag  or  parcel 
offered  for  sale  the  percentage  of  nitrogen  (or  ammonia), 
available  phosphoric  acid  and  potash.  The  enforcement  of  the 
law  and  the  chemical  examination  of  the  fertilizers  to  determine 
if  they  agree  with  the  guarantee,  rests  with  the  State  Experiment 
Station,  or  in  some  states  with  the  State  Department  of  Agricul- 
ture. The  results  secured  are  published  in  bulletins  available 
to  the  farmers  of  the  state,  and  should  be  consulted  freely  by 
those  buying  such  materials.  These  laws  have  resulted  in  almost 
complete  disappearance  of  materials  compounded  with  the  in- 
tention of  defrauding,  as  well  as  a  great  lessening  in  the  number 
of  brands  offered  for  sale.  Nevertheless,  statements  often  ap- 
pear on  the  bags,  which,  to  say  the  least,  are  confusing  and  may 
mislead  the  buyer.  Phosphoric  acid,  10  per  cent,  for  example, 
is  often  stated  as  equivalent  to  bone  phosphate,  22  per  cent.  To 
the  buyer  the  higher  figure  is  attractive  and  he  is  led  to  believe 
1hat  he  will  obtain  something  more  than  the  10  per  cent  of  phos^ 


1  ,  j  Agricultural  Chemistry. 

phoric  acid  guaranteed.     The  following  example,  taken  from  the 
label  of  a  fertilizer  bag,  will  explain  this  point  more  fully : — 

GENERAL    CROP   BRAND. 

Guaranteed  Analysis. 

Nitrogen 0 . 82 —  1 . 65  per  cent 

Ammonia 1.0  —  2.0 

Available  Phosphoric  Acid K.O  —10.0          " 

Equal  Bone  Phosphate 17.0  —21 .0 

Total  Phosphoric  Acid 10.0  —12.0 

Potash  Sulphate 11.0  —13.0 

Potash (U)  —  7.0 

Color  not  guaranteed. 

The  buyer  is  only  concerned  in  the  total  amount  of  nitrogen, 
available  phosphoric  acid  and  potash  that  the  brand  contains, 
and  these  figures  alone  should  dictate  the  actual  worth  of  the 
material. 


CHAPTER  VIII 
CROPS. 

Having  considered  somewhat  in  detail  the  chemical  composi- 
tion of  plants  and  the  functions  of  the  chemical  elements  con- 
cerned in  their  growth,  we  are  in  a  position  to  discuss  in  general 
terms  the  relative  composition  and  food  requirements  of  crops, 
and  the  factors  influencing  their  composition  and  feeding  value. 
For  the  sake  of  convenience,  the  common  crops  will  be  considered 
under  the  following  arbitrary  divisions: — 

I.     Seed  crops — including,  , 

a.  Cereal  grains,  such  as  wheat,  corn,  rye,  barley,  oats 

and  rice. 

b.  Leguminous  seeds,  such  as  beans,  peas,  cowpeas    cnncl 

soy  beans. 

c.  Miscellaneous  seeds,  such  as  cotton  seed,  flaxseed.  ens- 

tor  beans  and  others. 
II.     Hay  or  fodder  crops — including, 

a.  Common  grasses,  such  as  timothy,  red  top  and  Ken- 

tucky blue  grass. 

b.  Cereal  plants,  such  as  corn,  oats,  barley    and  other 

crops,  cut  at  an  immature  stage  f<5r  soiling  pur- 
poses, silage,  or  hay. 

c.  Leguminous  crops,  such   as  alfalfa  and  the  various 

clovers  (which  form,  true  hays),  and  the  pea,  cow 
pea,  vetch  and  soy  bean  (when  cut  green  for  soiling 
purposes  or  for  curing  as  hays). 
Root  crops — including, 

a.  True  roots,  such  as  mangels,  turnips,  beets  and  carrots. 

b.  Tubers,  or  subterranean  stems,  such  as  potatoes. 
IV.     Fruit  crops — including, 

a.  Fruit  of  perennial  plants,  such  as  the  apple,  pear, 
plum,  peach,  grape  and  most  berries,  as  well  as  the 
orange,  lemon,  banana  and  other  tropical  fruits. 


174 


Agricultural  Chemistry. 


b.     Fruit   of  annual   plants — such   as  melons,   pumpkin. 

squash  and  tomato. 
V.     Forest  growth — including, 

hardwooded  and  softwooded  perennial  plants. 
V I .     Miscellaneous  crops — including, 

tobacco,  and  the  onion,  cabbage,  and  other  truck  crops. 

In  considering  the  seed  crops  we  must  take  into  account  the 
straw  as  well  as  the  grain.  The  former  portion  of  these  crops 
is  not  important  in  all  cases  as  a  feeding  material,  but  it  always 
stands  responsible  for  a  part  of  the  exhaustion  of  plant  food 
from  the  soil.  For  this  reason  the  tops  as  well  as  the  roots  of 
root-crops  should  be  considered. 

The  yield  of  crops,  both  in  the  total  substance  produced  and 
in  its  proportion  of  plant  compounds,  varies  widely.  These  fac- 
tors control  to  a  large  extent  the  value  of  the  crops  as  feeding- 
stuffs,  and  their  demands  upon  the  plant  food  constituents  of 
the  soil.  A  rational  comparison  of  the  composition  of  crops  can 
be  made  only  upon  the  basis  of  yield  of  dry  matter  and  of  the 
individual  nutrient  compounds  or  groups  of  compounds  con- 
tained therein,  per  acre.  The  following  table  gives  the  total 

Yield  in  Pounds  Per  Acre. 


Fresh 
material 

Dry 
matter 

Crude 
protein 

N.  free 
extract 

Ether 
extract 

Crude 
fiber 

Ash 

Alfalfa  

35,000 
30  000 

9,870 
6  270 

1,680 
510 

4,305 
3  300 

350 

240 

2,590 
1  800 

945 
420 

Red  clover  

18,000 

5,256 

792 

2  430 

198 

1,458 

378 

Timothy 

11  500 

4  416 

356 

2  323 

138 

1  357 

231 

Hungarian  grass.  .  . 
Mangels 

19,000 
60  000 

3,591 
5  400 

589 
840 

2,698 
3  3CO 

133 
120 

1,748 
540 

323 
660 

Sugar  beets  
Potatoes  
Oats  

32,  (XX) 
18,000 
1,120 

4,320 

3,798 
995 

570 
378 
132 

3,  136 
3,114 
668 

32 

18 
56 

288 
104 
106 

288 
180 
33 

Oat  straw  

4,000 

3  672 

160 

1  696 

92 

1  480 

204 

I'.urley  

1     "IK) 

1  069 

147 

837 

21 

32 

?8 

Harle'v  straw  
(  /nbbage  

4,000 
18  460 

3,432 

4  NOO 

140 

i    200 

1,560 
1   900 

60 
•200 

1,400 
750 

228 
7(10 

Tobacco   (leaf).... 

12,840 

1,730 

300 

935 

51 

263 

321 

Crops.  175 

yields  and  the  yields  of  proximate  constituents  of  such  compara- 
ble amounts  of  crops. 

The  differences  between  weights  of  fresh  material  and  of  dry 
matter  in  the  above  table  are  due  almost  entirely  to  water  lost 
in  the  process  of  complete  curing  or  drying.  For  example,  corn 
in  the  green  state  consists  of  nearly  80  per  cent  of  water,  potatoes 
have  about  the  same  amount,  sugar  beets  contain  about  86  per 
cent,  and  mangels  consist  of  over  90  per  cent  of  this  constituent. 
The  several  hay  crops  of  the  preceding  table  are  rather  lower  in 
water,  containing  from  60  to  a  little  over  70  per  cent.  This 
amount  is  greatly  reduced  by  the  curing  process  so  that  the  hays 
contain  only  from  10  to  20  per  cent. 

The  field  cured  grain  crops  carry  from  7  to  9  per  cent  of 
moisture  in  the  straw  and  about  11  per  cent  in  the  seed.  The 
high  water  content  of  some  of  these  crops,  aside  from  its  detri- 
mental effect  upon  keeping  qualities,  is  sometimes  of  importance 
with  reference  to  economy  of  transportation.  For  example, 
since  the  root  crops  retain  most  of  their  original  water  content 
during  proper  storage,  it  is  evident  that  a  given  amount  of  dry 
food  material  is  handled  far  less  economically  in  them  than  in 
grains  and  hays.  It  will  be  observed  that  the  enormous  acre- 
yields  of  these  crops,  particularly  of  the  mangel,  are  reduced  to 
moderate  figures  when  considered  in  terms  of  dry  matter. 

The  high  protein  content  of  the  legume  hays  (clover  and  al- 
ifalfa)  is  in  marked  contrast  to  the  amount  of  this  group  of  con- 
istituents  in  the  common  hays  and  the  cereal  crops.  This  differ- 
!  ence  will  be  discussed  in  detail  in  the  consideration  of  individual 
crops.  Mangels  also  contain  a  high  percentage  of  "  crude  pro- 
tein ;"  but  it  has  been  shown  that  more  than  one-half  of  the 
nitrogen  upon  which  this  figure  is  based  is  not  in  the  form  of 
protein  but  is  contained  in  amide  compounds.  This  is  probably 
true  for  other  root  crops,  and  greatly  diminishes  their  apparent 
protein  value. 

With  reference  to  the  production  of  fat,  it  should  be  stated 
that  while  the  grains  may  yield  quite  pure  fats  to  the  chemist's 


176  Agricultural  Chemistry. 

method  of  analysis,  this  will  be  far  from  true  in  the  case  of  hays 
and  straws.  Considerable  amounts  of  chlorophyll  will  contam- 
inate the  "crude  fats"  determined  for  the  hay  crops.  The  high 
yield  of  ether  extract  in  alfalfa  hay,  as  in  the  case  of  other  con- 
stituents of  this  crop,  is  incident  to  a  large  total  yield  of  dry 
matter  obtained  from  the  several  successive  cuttings  per  season. 
In  this  respect,  this  crop  possesses  a  marked  advantage  in  com- 
parison with  the  others. 

A  large  proportion  of  the  ash  of  cereal  straws,  some  of  the 
cereal  grains,  and  the  common  hays,  consists  of  non-essential 
silica.  The  legumes  and  root-crops  in  general,  however,  are  very 
low  in  this  constituent.  The  excessive  ash  content  of  alfalfa,  the 
mangel,  the  cabbage  and  other  crops  is  notable ;  being  composed 
chiefly  of  such  essential  constituents  as  lime,  potash,  and  phos- 
phoric acid,  it  has  a  significant  bearing  upon  the  well-known  ex- 
haustive effects  of  these  crops  upon  the  soil,  f  A  knowledge  of  the 
amount  and  composition  of  the  ash  of  crops  gives  a  basis  for  the 
selection  of  animal  rations,  well-balanced  in  ash  constituents.  ) 

The  relative  drain  of  some  crops  upon  the  soil  is  shown  by  tne 
table  in  the  appendix  quoted  from  Warington.  The  figures 
i'l-i-  sulphur  trioxide  have  been  corrected  in  most  cases  on 
the  basis  of  determinations  made  at  the  Wisconsin  Experiment 
Station.  The  older  determinations  of  sulphur  by  analysis  of 
the  ash  have  been  shown  to  be  low.  Other  data  have  been  com- 
piled from  various  sources  and  added  to  Warington 's  table. 

The  food  requirements  of  cereal  grains,  as  shown  by  a  general 
survey  of  the  table,  are  not  widely  variant.  It  will  be  observed 
that  the  ash  constituents  are  uniformly  much  higher  in  the  straw 
than  in  the  grain.  Nitrogen,  on  the  other  hand,  accumulates 
chiefly  in  the  grain,  about  two-thirds  of  the  total  nitrogen  re- 
moved being  found  in  this  part  of  the  crop.  The  separate  con- 
stituents of  the  ash  show  great  differences  in  their  relative  dis- 
tribution between  grain  and  straw.  Thus,  while  potash,  soda, 
lime,  chlorine  and  silica  are  located  chiefly  in  the  straw,  the 
greater  part  of  the  phosphoric  acid  occurs  without  exception  in 


Crops.  177 

sulphur  trioxide  and  magnesia  are  quite  evenly 
divided  between  the  two  parts  of  the  crop. 

Nitrogen  and  phosphoric  acid  are  probably  the  plant  food  con- 
stituents most  frequently  lacking  in  soils  and  in  many  cases  their 
depletion  is  to  be  attributed  to  continuous  raising  and  selling  of 
grain  crops.  It  is  evident  that  either  the  manure  from  grains 
fed  on  the  farm  should  be  carefully  husbanded,  or  equivalent  re- 
turns of  plant  food  to  the  farm  should  be  made  by  the  purchase 
of  feeding  stuffs  or  fertilizers.  This  subject  has  been  fully  dis- 
cussed in  the  chapter  on  Manures.  It  applies  with  particular 
emphasis  to  cereal  crops,  because  they  are  wholly  dependent  up- 
on stores  of  available  nitrogen  in  the  soil  for  their  supply  of  this 
element  arid  generally  thrive  best  when  supplied  with  available 
forms  of  phosphoric  acid. 

The  conservation  of  the  smaller  amounts  of  plant  food  in  cereal 
straws  likewise  should  not  be  neglected.  The  practice  of  dis- 
posing of  these  straws  by  burning  is  a  wasteful  one,  for  by  this 

?atment  the  nitrogen  which  they  contain  is  entirely  lost. 

Food  requirements  of  the  common  grasses.     The  common 

lys,  represented  in  our  table  by  meadow  hay,  are  essentially 
straw  crops,  and  their  food  requirements  practically  duplicate 
those  of  the  cereal  crops.  Hays  of  the  legumes  show  marked 
differences  from  the  true  hays.  While  for  example,  clover  hay 
removes  twice  as  much  nitrogen  from  the  land  as  do  the  cereal 
crops  or  meadow  hay,  it  should  be  borne  in  mind  that,  like  other 
legumes,  this  crop  obtains  almost  all  its  nitrogen  from  the  air 
through  the  activity  of  bacteria  living  in  association  with  its 
roots.  As  will  be  demonstrated  further  on,  these  crops  increase 
rather  than  diminish  the  supply  of  nitrogen  in  the  soil. 

The  true  legume  hays  develop  extensive  root  systems  and  draw 
heavily  upon  the  ash  constituents  of  the  soil.  This  applies  in  a 
limited  degree  to  phosphoric  acid,  but  more  particularly  to  potash 
and  lime,  which  form  one-half  the  total  ash  of  the  bean  crop,  two- 
thirds  of  the  ash  of  clover  hay,  and  nearly  as  large  a  proportion 
in  the  case  of  alfalfa  hay.  The  legume  family  of  plants  is  es- 


178  Agricultural  Chemistry. 

pecially  sensitive  to  acid  conditions  of  the  soil.  This  is  probably 
because  such  a  medium  is  unfavorable  for  the  activity  of 
nitrogen-fixing  bacteria.  This  condition  cannot  develop  in  a  soil 
properly  stocked  with  lime. 

The  leguminous  grain  crops  such  as  beans  or  peas  are  less  ex- 
hausting tft  the  minerals  of  the  soil  than  are  the  hays  of  legumes, 
for  they  develop  a  less  extensive  root  system.  These  crops  show 
the  same  general  distribution  of  constituents  between  the  grain 
and  straw  as  do  the  cereal  crops,  and,  as  with  the  latter  crops, 
the  greater  part  of  the  nitrogen  and  phosphoric  acid  is  removed 
in  the  seed. 

Requirements  of  root  crops.  The  true  root  crops  are  pre- 
eminently soil- exhausting  crops.  Not  only  do  they  assimilate 
greater  amounts  of  ash  constituents  per  acre  than  the  other 
crops  removed  from  the  soil,  with  the  exception  of  alfalfa,  but 
they  remove  more  nitrogen  than  the  cereals  or  grasses.  In  the 
case  of  turnips,  this  amount  of  nitrogen  is  seen  to  be  twice  that 
removed  by  cereal  grains  or  meadow  hay,  and  in  the  case  of 
mangels,  it  is  three  times  as  much  as  these  crops  contain.  It  is 
important  to  realize  that  the  root  crops  are  entirely  dependent 
upon  the  soil  for  this  important  element  of  plant  food.  Potash 
is  uniformly  conspicuous  for  its  high  proportion  in  the  ash  of 
these  crops.  Its  presence  is  explained  by  the  fact  already  ob- 
served, that  this  mineral  is  essential  to  the  production  of  starch 
and  sugar,  which  are  predominant  compounds  in  these  crops. 
Since  the  amounts  of  phosphoric  acid  removed  by  these  crops  are 
also  uniformly  high,  it  is  apparent,  as  demonstrated  also  by  prac- 
tice, that  they  require  especially  complete  and  heavy  manuring 
when  grown  under  intensive  cultivation. 

Requirements  of  fruit  crops.  This  class  of  crops  is  less  ex- 
haustive and  less  dependent  upon  immediate  manuring  than  the 
crops  already  discussed;  the  individual  requirements  will  be 
considered  later. 

Requirements  of  forest  growth.  Timber  growth  exceeds  most 
of  the  other  crops  discussed  in  the  annual  production  of  dry  mat- 


Crops. 


179 


ter,  but  this  increase  is  obtained  at  small  expense  in  plant  food. 
According  to  Warington,  the  production  of '3000  pounds  of  dry 
pine  timber  requires  the  consumption  of  only  2%  pounds  of 
potash  and  1  pound  of  phosphoric  acid  per  acre  yearly.  Harder 


Note  the  difference  in  the  extent  of  the  root  system  of  the  two  plants, 
alfalfa  and  barley. 

woods  require  rather  more  of  these  constituents.  The  amount  of 
nitrogen  in  wood  is  very  small,  amounting  to  an  average  of  about 
10  pounds  for  an  annual  growth  of  beech  wood.  Trees  produce 
seed  only  at  mature  age  and  then  at  the  expense  of  material 
stored  in  the  leaves  and  wood. 


180  Agricultural  Chemistry. 

The  litter  which  accumulates  during  the  earlier  years  of 
growth  will  therefore  be  most  effective  in  increasing  the  value  of 
the  surface  soil  by  stores  of  plant  food  obtained  from  the  deeper 
soil  layers.  As  a  result  of  this  process,  the  manurial  require- 
ments of  the  forest  are  low  and  become  much  smaller  than  in 
ordinary  cropping. 

Requirements  of  truck  crops.  The  various  truck  crops  differ 
widely  in  productiveness  and  feeding  habits.  Of  the  more  im- 
portant ones,  the  cabbage  assimilates  large  amounts  of  ash  con- 
stituents, with  the  exception  of  silica.  The  heavy  yield  desired 
with  such  crops  entails  a  correspondingly  high  consumption  of 
nitrogen  and  necessitates  heavy  manuring  with  this  element,  as 
well  as  liberal  manuring  with  potash  and  phosphoric  acid.  The 
high  content  of  sulphur  tri-oxide  in  this  crop  and  in  the  turnip 
and  other  members  of  the  cruciferae,  suggests  that  in  some  cases 
this  element  may  become  the  limiting  factor  in  plant  growth,  and 
that  the  beneficial  effects  sometimes  observed  from  the  applica- 
tion of  gypsum  may  be  due  to  the  sulphur  tri-oxide  which  it 
supplies. 

The  tobacco  crop  is  a  comparatively  light  feeder,  but  makes 
positive  demands  for  nitrogen,  potash  and  lime. 

Crop  residues,  which  include  the  leaves  of  root  crops,  the 
straws  of  grain  crops,  the  stalks  of  tobacco  and  waste  parts  from 
trimming,  contain  sufficient  plant  food  to  justify  the  exercise  of 
care  to  return  them  to  the  soil.  Potash  and  lime  are  the  con- 
stituents of  most  concern  in  the  straws  and  they  are  of  even 
greater  consequence  in  the  leaves  of  root  crops.  The  common 
practice  of  spreading  tobacco  stalks  to  decay  upon  the  land, 
makes  possible,  as  indicated  by  the  table,  the  returning  of  con- 
siderable amounts  of  potash  and  also  of  nitrogen  to  the  soil. 
These  crop  residues  are  frequently  reduced  to  ashes  to  economize 
labor  in  their  disposal,  but  this  practice  should  be  discouraged, 
since  it  involves  a  loss  of  much  nitrogen. 

Whenever  the  soil  will  profit  by  the  addition  of  organic  mat- 
ter, these  materials  should  be  turned  in  whole.  Another  prac- 


^  Craps.  181 

tice,  much  better  than  burning,  is  to  compost  such  material  with 
soil.  In  this  way,  both  nitrogen  and  the  ash  constituents  are 
conserved  as  the  organic  matter  decays. 

Individual  characteristics  of  crops  may  be  taken  up  now  more 
in  detail. 

Wheat.  This  important  grain  represented  25  per  cent  of  the 
value  of  cereal  crops  and  13  per  cent  of  all  crops  in  1900.  Sixty- 
two  per  cent  of  the  cereal  products  milled  in  that  year  were  from 
wheat.  Over  one-third  of  the  farms  in  the  United  States  raised 
wheat,  with  a  total  production  in  1900  of  35  billion  bushels. 
Extensive  breeding  of  this  grain  has  led  to  the  production  of 
about  245  leading  varieties. 

The  crop  is  commonly  sown  in  the  fall  and  grown  as  "winter 
wheat."  As  a  result,  it  has  a  longer  period  of  growth  and  a 
more  extensive  root  system  than  most  of  the  cereals.  The  roots, 
which  are  especially  developed  in  Durum  wheat,  have  been  found 
to  reach  a  length  of  four,  and  even  of  six  feet.  These  conditions 
enable  the  plant  to  feed  effectively  upon  the  soil.  The  necessary 
omission  of  spring  tillage  in  the  case  of  this  crop,  prevents  the 
aid  of  this  important  stimulus  to  nitrification  and  renders  wheat 
dependent  largely  upon  manurial  supplies  of  available  nitrogen. 
Its  extensive  root  system  and  long  period  of  growth  aid  this  plant 
in  deriving  its  mineral  constituents  from  the  soil  and  make  it 
more  independent  of  available  potash  or  phosphate  fertilization ; 
nitrates  or  ammonium  salts  consequently  are  recommended  as  the 
chief  fertilizer  treatment. 

The  wheat  kernel,  according  to  Bessey,  is  separated  mechan- 
ically into  the  following  proportion  of  parts : — 

Coatings  (or  bran  layers) 5         per  cent 

Gluten  layer 3—4        " 

Starch  cells 84—86 

Germ 6  " 

Protein  and  fat  are  highest  in  the  germ  and  bran,  ash  is  high- 
est in  the  bran,  and  the  fibre  is  confined  almost  exclusively  to 
this  coating.  Starch  is  the  characteristic,  and  by  far  the  most 


182  Agricultural  Chemistry. 

abundant  constituent  in  wheat,  as  it  is  in  all  the  cereal  grains. 
This  constituent  is  highest  in  the  flour,  which  represents  the  in- 
terior of  the  kernel.  (The  composition  of  grains  and  other  crops 
and  of  their  more  important  products  will  be  found  in  tables  in 
the  Appendix. ) 

It  is  a  significant  fact  that  about  80  per  cent  of  the  phosphoric 
acid  of  this  grain  is  located  in  the  bran.  This  makes  possible 
the  return  of  much  of  this  important  constituent  to  the  farm  in 
wheat  bran  and  its  eventual  recovery  in  the  manure.  The  gluten 
or  gum-forming  portion  of  the  wheat  grain  is  composed  of  two 
proteins,  glutenin  and  gliadin,  which  form  about  85  per  cent  of 
the  total  proteins  of  the  seed.  The  tenacity  of  bread  dough  and 
of  macaroni  made  from  wheat  flour,  is  due  to  gliadin.  Consid- 
erable attention  has  been  given  to  the  factors  affecting  the 
amount  and  composition  of  gluten  in  wheat  and  to  the  conse- 
quent milling  qualities  of  the  grain  and  baking  qualities  of  the 
flour.  According  to  Snyder,  the  most  valuable  wheats  for  bread 
making  purposes  are  those  in  which  80  to  85  per  cent  of  the 
protein  is  gluten  and  the  gluten  is  composed  of  from  60  to  65 
per  cent  of  gliadin  and  35  to  40  per  cent  glutenin. 

Wheat  straw  has  little  value  to  the  stock  feeder  except  as  lit- 
ter. Experiments  have  shown  that  when  consumed  it  leaves 
little  surplus  of  food  value  to  the  animal  above  the  energy  re- 
quired for  mastication  and  digestion.  But  when  the  straw  is 
pulped  by  the  process  commonly  used  in  paper  making,  the 
residual  tissue  has  been  shown  to  have  a  food  value  equal  to  that 
of  starch.  The  plant  food  in  the  straw  should  be  saved  by  utiliz- 
ing it  as  litter  or  composting  in  the  manner  already  described. 

Rye,  like  wheat,  is  sown  chiefly  in  the  fall.  It  closely  re- 
sembles the  latter  in  its  composition  and  habits  of  growth.  The 
growth  of  this  crop  in  early  spring  may  be  stimulated  by  adding 
TOO  to  150  pounds  of  nitrate  of  soda  per  acre. 

Rye  grain  is  slightly  lower  in  fat  and  protein  than  is  wheat. 
Its  gluten  is  not  so  well  suited  for  bread  making  as  that  of  wheat, 
but  rye  flour  produces  a  coarse  bread  which  is  consumed  to  a 


Crops.  183 

considerable  extent.  The  straw  of  this  crop  is  high  in  fibre  and 
the  nutrient  compounds  which  it  contains  are  less  digestible  than 
those  of  oat  or  barley  straws,  so  that  it  possesses  little  feeding 
value. 

Barley  has  been  developed  into  many  varieties,  which  fall 
mostly  into  either  the  two  rowed  or  the  six  rowed  type.  It  may 
be  sown  in  the  fall  and  wintered,  but  it  is  more  distinctly  a 
sprinir  crop  than  is  rye  or  wheat.  It  is  hardier  than  the  latter, 
being  adapted  to  wider  ranges  of  latitude  and  climate.  The 
crop  grows  rapidly  and  is  more  exhaustive  of  surface  soil  miner- 
als than  the  cereals  already  discussed,  because  of  the  limited  feed- 
ing area  of  its  root  system.  This  limitation,  together  with  its 
comparatively  short  period  of  growth,  makes  the  crop  more  de- 
pendent upon  liberal  manuring  than  are. wheat  or  rye.  Spring 
tillage,  however,  aids  nitrification  and  reduces  the  requirement 
for  available  nitrogenous  manures.  Its  comparatively  limited 
root  system  and  short  time  of  growth  makes  it  especially  respon- 
sive to  soluble  phosphate  manuring.  Excessive  supplying  of 
nitrogen  to  this  crop  is  to  be  avoided,  not  only  because  of  the 
coarse  rank  growth  which  it  induces  at  the  expense  of  seed  pro- 
duction, but  also,  because  the  high  protein  content  of  the  grain, 
consequent  upon  such  manuring,  unfits  it  for  malting  purposes. 

Barley  is  richer  than  wheat  in  ash,  fibre  and  protein;  the 
former  two  constituents  are  largely  contributed  by  the  hull 
of  this  grain.  It  is  slightly  poorer  in  fat  and  carbohydrates  than 
is  wheat.  Barley  gluten  does  not  possess  the  property  required 
for  bread  making,  and  consequently  the  grain  finds  only  a  lim- 
ited use  for  human  food.  It  is  fed  to  horses  and  cattle  and  is 
highly  esteemed  for  the  production  of  pork. 

The  production  of  malt  from  barley  gives  this  grain  its  chief 
value.  To  produce  this,  the  grain  is  soaked  in  water  for  some 
time  and  spread  upon  floors  in  thick  layers.  Germination  en- 
sues and  heat  is  evolved  in  the  process.  When  the  sprouts  are 
about  one-half  inch  long,  the  grain  is  heated  sufficiently  in  an 


184  Agricultural  Chemistry. 

oven  to  kill  the  embryo.  The  sprouts  are  then  removed,  dried 
and  ground,  and  put  upon  the  market  as  a  feeding-stuff  under 
the  name  of  "malt  sprouts."  The  remaining  grain,  known  as 
"malt,"  does  not  differ  much  in  composition  from  the  original 
barley ;  but  the  germinating  process  has  produced  and  activated 
an  enzyme  of  the  seed,  known  as  "diastase."  If  the  malt  is 
heated  now  with  water  for  some  time  at  120°  F.,  a  process  known 
as  ' '  mashing, ' '  this  enzyme  converts  the  starch  of  the  grain  into 
soluble  carbohydrates.  Diastase  has  been  found  capable  of  thus 
transforming  2000  times  its  own  weight  of  starch  into  dextrines 
or  maltose.  Since  the  amount  of  this  enzyme  in  barley  is  capable 
of  transforming  much  more  starch  than  is  associated  with  it, 
unmalted  barley  or  other  starchy  grains,  such  as  corn,  are  fre- 
quently added  to  the  mash.  The  maltose  produced  in  this  man- 
ner, together  with  other  substances,  is  dissolved  in  the  liquor  of 
the  mash  and  may  be  drawn  off  and  seeded  with  the  proper  yeast 
to  undergo  alcoholic  fermentation.  This  fermentation  results 
in  the  production  of  beer  and  other  liquors. 

The  residual  grain,  which  contains  the  fat  and  protein  orig- 
inally present,  is  placed  upon  the  feeding  stuff  market  as  "wet 
or  dried  brewers'  grains."  The  latter  form  is  preferred  for 
its  more  economical  handling  and  better  keeping  qualities. 

Barley  straw,  when  used  in  feeding  experiments,  has  been 
shown  to  be  more  completely  digested  by  ruminants  than  is  the 
straw  of  wheat  or  rye,  thus  giving  it  a  limited  value  for  feeding 
purposes.  This  fact  has  also  been  demonstrated  by  practice. 

Oats  is  also  a  crop  which  spring  sowing  and  tillage  aids. 
The  spring  tillage,  in  preparing  the  land  for  sowing,  acts  as  ail 
aid  to  nitrification  and  makes  it  unnecessary  to  apply  the  directly 
available  nitrogenous  fertilizers.  But  its  short  growing  season 
renders  it  dependent  upon  liberal  manuring  to  produce  max- 
imum yields.  Excess  of  nitrogenous  manure  should  be  avoided 
because  of  the  disastrous  results  from  over-development  of  the 
foliage  of  the  crop.  Much  of  the  "lodging"  of  oat  crops  on 


Crops.  185 

heavy  soils  is  probably  due  to  excessive  production  of  nitrates 
from  humus  or  manure,  Avhich  induces  a  rank  growth  of  weak- 
stemmed  plants. 

Oat  grain  consists  of  approximately  70  per  cent  kernel  and 
30  per  cent  hull.  The  large  proportion  of  hulls  accounts  for  the 
high  fiber  and  ash  content  of  the  grain  and  reduces  its  digest- 
ibility. On  the  other  hand  it  appears  to  be  of  value  for  its 
mechanical,  laxative  effect  upon  the  digestive  tract.  This  grain 
is  notable  among  the  cereals  on  account  of  its  high  content  of 
fat.  The  ground,  hulled  kernels,  known  as  "oatmeal,"  is  much 
used  for  "breakfast  foods."  The  residual  grain  and  poorer 
kernels  are  worked  into  oat  feeds.  Whole  oats  is  much  prized  by 
the  horse  feeder.  It  has  been  supposed  that  the  grain  possesses 
peculiar  tonic  properties,  due  to  a  specific  compound,  but  there 
are  no  scientific  data  in  support  of  this  view. 

Oat  straw  is  more  palatable  than  the  other  cereal  straws  and 
possesses  some  value  as  a  food  for  cattle  and  sheep. 

Corn,  or  maize,  has  formed  over  50  per  cent  of  the  acreage 
of  cereals  in  the  United  States  for  several  decades.  In  1900  it 
formed  56  per  cent  of  the  value  of  cereals  and  28.5  per  cent  of 
the  value  of  all  crops.  The  white  man  discovered  it  under  cul- 
tivation by  the  American  Indian  and  gave  to  it  the  name  Indian 
corn.  Continuous  breeding  has  developed  many  improved  va- 
rieties, which  differ  widely  in  size,  form,  color  and  chemical  com- 
position. The  common  varieties  of  corn  fall  under  three  sub- 
species :  dent,  flint  and  sweet  corn.  By  far  the  greatest  number 
of  varieties  are  of  the  dent  species.  This  species  derives  its  name 
from  the  characteristic  indentation  of  its  crown,  due  to  shrinkage 
of  the  starch  cap  as  the  grain  dries.  Flint  corn  is  characterized 
by  a  smooth,  firm  coat,  supported  by  a  layer  of  hard  or  horny 
starch,  so  that  the  grain  retains  its  shape  as  it  dries.  Sweet  corn 
is  characterized  by  a  high  percentage  of  sucrose  and  develops  a 
prominently  wrinkled  surface,  as  a  result  of  shrinkage  in  drying. 

Examination  of  a  longitudinal  section  of  a  corn  grain  made 
by  splitting  it  across  the  thin  dimension,  shows  it  to  consist  of 


186  Agricultural  Chemistry. 

four  prominent  parts,  as  follows: — germ,  light  colored  starch 
cells,  dark  gluten  layers  and  a  thin  outer  coating.  The  germ  is 
located  at  the  tip  of  the  kernel  and  is  more  or  less  completely 
surrounded  by  starch,  which  forms  the  floury  portion  of  the 
grain.  Outside  the  starch,  nearly  or  completely  surrounding  it 
and  more  or  less  blending  with  it,  is  the  yellowish  gluten  layer. 
The  whole  kernel  is  coverd  by  a  thin  coating  which  forms  a  small 
amount  of  bran  in  the  milling  process.  The  germ  contains  most 
of  the  fat  of  the  corn  grain,  while  the  gluten  is  the  portion  richest 
in  protein.  That  portion  of  the  starch  bordering  upon  the  gluten 
layer  differs  in  character  from  the  common,  floury  starch,  and  is 
known  as  "horny"  or  "glossy"  starch.  Almost  all  of  the  starch 
of  popcorn  is  of  this  variety. 

Corn  is  slightly  lower  in  protein  and  much  higher  in  fat  than 
is  wheat.  The  latter  constituent  is  sometimes  separated  from  the 
grain  on  a  commercial  scale  as  corn-oil.  Corn  meal  is  low  in 
fiber  and  pentosans,  the  carbohydrates  being  nearly  limited  to 
starch.  As  a  result,  corn  is  used  extensively  in  the  production 
of  sugar  by  the  process  already  described  under  "glucose,"  the 
commercial  product  being  known  as  "corn  syrup."  The  residue 
from  this  process  is  sold  for  stock  feeding  as  "gluten  feed."  To 
a  limited  extent,  it  is  also  separated  into  such  fancy  feeds  as 
"corn  bran,"  "gluten  meal"  and  "germ  oil  meal." 

The  corn  grain  is  low  in  ash,  containing  but  1.5  per  cent,  and 
extremely  deficient  in  lime;  this  constituent  forms  only  about 
2.3  per  cent  of  the  ash,  or  0.03  per  cent  of  the  grain.  It  is  thus 
apparent  that  corn  alone  forms  an  incomplete  ration  for  grow- 
ing animals  using  grain  alone,  such  as  swine. 

Corn  is  a  shallow  rooted  crop  and  requires  liberal  manuring. 
It  has  the  advantage,  however,  of  a  late  summer  growth,  so  that 
it  has  the  opportunity  of  assimilating  the  nitrates  produced  dur- 
ing the  hot  season.  Fresh  farm  manure  should  be  applied  to 
corn,  as  to  most  of  the  cereals,  at  the  rate  of  8  to  10  tons  per  acpft 

Rice  has  been  estimated  to  be  the  chief  food  of  over  one-half 
of  the  human  race.  It  differs  from  the  other  grain  crops  in  re- 


Crops.  187 

quiring  a  warm  climate  and  abundance  of  water,  hence  it  is 
usually  grown  under  irrigation.  When  so  grown  it  yields  two 
crops  and  requires  liberal  manuring.  Since  nitrification  is  sup- 
pressed on  rice  land,  nitrates  are  very  effective  with  this  crop. 
Composted  manures  are  used  for  the  crop  in  China  and  Japan. 

Rice  grain  is  extremely  low  in  ash,  fiber  and  fat,  and  contains 
but  about  7.4  per  cent  of  protein.  It  is  essentially  a  carbohyd- 
rate food,  nearly  80  per  cent  of  it  being  starch.  The  rice  of 
commerce  is  a  product  of  a  milling  process  which  removes  the 
outer  husk  from  the  grain  and  yields  as  by-products,  rice  polish 
and  rice  bran.  The  former  is  fine  and  floury  and  much  richer 
than  the  grain  in  ash,  protein  and  fat,  while  the  latter  is  a  coarse 
material  high  in  percentages  of  ash  and  fiber.  The  two  by- 
products are  usually  mixed  and  sold  as  rice-meal,  or  rice-feed. 
Like  wheat,  and  in  contrast  to  most  of  the  other  grains,  rice  car- 
ries a  large  share  of  its  phosphorus  compounds  in  the  outer 
coatings,  which  makes  possible  a  considerable  recovery  of  phos- 
phoric acid  with  the  manure  produced  from  rice  feeds. 

Leguminous  seeds  differ  chiefly  from  the  seeds  of  cereals  by 
a  higher  content  of  protein  and  a  correspondingly  lower  content 
of  carbohydrates.  This  does  not  involve,  as  already  pointed  out, 
a  heavy  demand  upon  the  soil  supplies  of  nitrogen.  Protein 
formation  in  these  crops,  however,  places  a  considerable  tax  upon 
the  ash  constituents  of  the  soil.  In  some  cases  the  carbohydate 
material  of  these  grains  has  been  found  to  consist  chiefly  of 
galactans,  a  class  of  compounds  already  discussed  under  the 
4  *  poly-saccharides "  of  the  plant.  Liberal  supplies  of  phosphoric 
acid,  lime  and  potash  are  required  for  these  crops.  A  number  of 
legumes  produce  seed  which  form  a  considerable  bulk  of  the  total 
crop.  This  is  true  of  the  soy-bean,  horse-bean  and  cowpea.  The 
several  varieties  of  the  true  bean  and  the  pea  are  the  only  seeds, 
however,  of  much  commercial  importance.  The  soy-bean  and 
peanut  seeds  are  distinguished  by  high  percentages  of  fat, 
amounting  to  about  17  and  45  per  cent  in  the  grains,  respectively. 


188  Agricultural  Chemistry. 

Beans  thrive  best  on  clayey  soils,  well  stocked  with  lime,  potash 
and  phosphoric  acid.  Several  varieties  are  consumed,  green  or 
mature,  as  vegetables  and  are  valued  for  their  high  protein  con- 
tent. The  soy-bean  was  introduced  from  Japan  and  soy-bean 
meal  finds  some  use  as  an  animal  feeding-stuff.  It  resembles  the 
bean  in  its  habits  of  growth. 

Peas  require  much  lime,  and  on  rich  soils  they  tend  to  produce 
luxuriant  vines  at  the  expense  of  seed.  The  fresh  seed  is  prized 
as  a  vegetable  and  cured  peas  are  valuable  for  pig  feeding.  It 
may  be  said  that  the  leguminous  crops  in  general  thrive  on  soils 
poor  in  nitrogen  but  well  supplied  with  the  other  elements  of 
fertility. 

Cotton-seed  is  one  of  several  miscellaneous  seeds  of  agricul- 
tural value.  The  seed  is  enveloped  by  the  lint  of  the  pod,  or 
"boll,"  of  the  plant.  American  cotton  yields  about  300  pounds 
of  lint  and  600  pounds  of  seed  per  acre.  The  seed  is  rich  in 
phosphoric  acid,  nitrogen  and  potash  and  the  crop  requires  ma- 
nurial  applications  of  these  constituents  in  the  order  given.  Cot- 
ton-seed oil  is  extracted  from  the  seed  by  pressure  and  also  by  the 
use  of  naphtha  as  a  solvent.  The  outer  coating,  or  hull,  of  the 
seed  is  generally  removed  previous  to  pressing,  in  which  case  the 
residue  is  known  as  "decorticated  cotton  cake,"  or,  when  ground, 
as  "cotton-seed  meal."  A  high  proportion  of  hulls  produces  a 
dark  colored  meal  and  lowers  its  digestibility  and  food  value. 
The  meal  is  somewhat  valued  for  feeding  because  of  its  high  pro- 
tein content,  but  because  it  contains  some  toxic  substance,  its  use 
is  necessarily  restricted.  It  is  also  used  as  a  fertilizer,  supplying 
nitrogen  in  a  form  gradually  available  to  the  crop.  Incidentally, 
it  supplies  considerable  amounts  of  potash  and  phosphoric  acid. 

Flax  seed,  or  linseed,  thrives  under  much  the  same  environ- 
ment as  that  required  by  wheat.  Where  grown  for  fiber,  the 
crop  requires  a  moist,  temperate  climate,  such  as  is  found  in  Ire- 
land, the  northern  United  States  and  Canada;  but  seed  pro- 
duction requires  warmer  climates.  The  crop  produces  an  ave- 


Crops.  189    - 


rage  yield  of  about  850  pounds  of  seed  and  2000  pounds  of  straw. 
Flax  requires  considerable  amounts  of  phosphoric  acid,  potash 
and  lime,  with  sufficient  nitrogen  to  induce  vigorous  growth. 

Linseed  resembles  cotton-seed  in  composition,  but  contains 
about  one-half  as  much  fiber  arid  about  10  per  cent  more  fat, 
having  30  to  40  per  cent  of  the  latter  ingredient.  The  oil  is 
obtained  as  from  cotton  seed,  the  ground  residue  from  the  crush- 
ing method  being  known  as  "old  process"  linseed  meal,  or  "oil 
meal,"  while  that  obtained  by  solvents  is  known  as  "new  pro- 
cess" meal.  "Old  process"  meal  carried  8  to  12  per  cent  of  fat, 
while  the  new  process  of  extraction  leaves  only  2  to  4  per  cent 
of  this  constituent.  The  oil  obtained  from  flax  seed  of  the  region 
about  the  Baltic  Sea  in  Europe  is  preferred  in  the  paint  industry 
because  of  its  great  absorbing  power  for  oxygen.  Linseed  meal 
is  a  valuable  high-protein  food  for  stock. 

Hempseed  is  obtained  from  a  crop  resembling  flax  in  its  utility 
both  for  fiber  and  seed.  It  grows  best  in  a  temperate  climate 
and  resembles  corn  in  its  requirements  of  the  soil.  Hemp  yields 
500  to  1500  pounds  of  fiber  and  the  same  range  of  seed  per  acre. 
The  seed  is  used  as  poultry  food  and  the  oil  obtained  from  it 
is  sometimes  used  to  adulterate  linseed  oil. 

Buckwheat  has  much  the  same  composition  as  wheat.  It  has 
the  advantage  of  thriving  upon  comparatively  light,  poor  soils. 
It  finds  limited  use  in  animal  feeding  and  as  human  food. 

Rape  seed  is  sometimes  grown  for  the  production  of  "rape 
oil"  or  "colza  oil."  It  yields  over  40  per  cent  of  this  fat.  The 
residue  of  the  feed  is  used  as  manure,  because  it  lacks  relish  as 
a  cattle  food.  Rape  belongs  to  the  same  plant  family  as  the 
turnip  and  closely  resembles  it  in  manurial  requirements. 

The  castor  bean  is  the  seed  of  a  plant  grown  in  some  local- 
ities as  a  crop,  in  others  for  ornamental  purposes,  while  in  some 
cases  it  is  looked  upon  as  a  weed.  In  the  temperate  zone  it  is 
an  annual,  but  in  the  tropics  it  is  a  perennial  tree  of  considerable 
size.  It  is  an  adaptable  plant  but  thrives  best  on  rich,  sandy 
soils.  The  seed  is  valued  for  oil,  which  it  contains  to  the  extent 


100  Agricultural  Chemistry. 

of  50  per  cent.  This  oil  finds  application  medicinally  and  as  a 
lubricant.  The  residue  of  the  seed  is  suitable  for  manure,  but 
cannot  be  used  for  feeding  because  of  its  poisonous  properties, 
due  to  a  powerfully  toxic  protein,  known  as  "ricin. " 

Sunflower  seed  is  produced  in  yields  of  about  50  bushels  per 
acre.  The  dry  seed  contains  20  per  cent  of  an  oil  sometimes  used 
as  a  substitute  for  olive  oil.  It  also  contains  30  per  cent  of  fiber 
and  16  per  cent  of  protein,  the  latter  giving  to  the  seed  and  its 
residue  some  value  as  poultry  and  cattle  feeds.  The  crop  pro- 
duces heavily  on  soils  high  in  fertility. 

Hays  or  fodder  crops  include  true  hays  which  are  cut  at  the 
blossoming  or  early  seeding  stage,  and  in  which  the  stems  so  pre- 
dominate in  bulk  as  to  make  them  practically  straw  crops.  They 
have,  in  fact,  the  same  general  composition  and  food  require- 
ments as  the  cereal  grains,  irrespective  of  seed  production.  Un- 
der this  class  also  fall  the  cereal  grains,  such  as  barley  or  oats, 
when  cut  while  succulent  for  soiling  purposes  or  hay  making,  and 
corn  and  other  crops  cut  for  silage.  These  differ  from  the  cereal 
straws  as  a  result  of  their  comparative  immaturity.  The  leg- 
uminous plants  in  this  role  differ  from  the  corresponding  legumes 
raised  for  seed  in  the  same  manner  as  indicated  for  cereal  plants. 
They  are  cut  at  an  immature  stage  of  growth  when  the  foliage 
far  outweighs  the  seed  in  amount  and  importance.  The  true 
hays  of  importance  are  comparatively  few  in  number. 

Timothy  is  perhaps  most  commonly  grown,  alone  or  associated 
with  clover.  It  is  representative  of  the  true  grasses,  as  a  class, 
being  high  in  fiber,  comparatively  low  in  protein,  and  rich  in 
potash  and  silica.  It  is  shallow  rooted  and  dependent  upon 
liberal  manuring.  It  grows  best  on  peaty  soils  and  hence  is  fav- 
ored by  heavy  applications  of  farm  manure.  The  application 
yearly  per  acre  of  90  to  180  pounds  of  nitrate  of  soda,  300  to  600 
pounds  of  bone  meal  and  70  to  140  pounds  of  chloride  or  sulphate 
of  potash  has  been  recommended  as  a  fertilizer  treatment. 

Red  top,  Hungarian  grass,  Kentucky  blue  grass  or  June 
grass,  orchard  grass  and  similar  hay  crops  resemble  timothy  in 


Crops.  191 

their  feeding  habits  and  composition  and  require  similar  manur- 
ing in  proportion  to  their  yield. 

Meadow  hay  and  pasture  grass  are  usually  a  mixture  of 
plants,  the  predominant  members  of  which  are  among  the  grasses 
already  described,  or  others  closely  related  to  them.  The  peaty 
nature  of  the  surface  soil  in  permanent  meadows  is  attributed  to 
the  decay  of  the  shallow  seated  root  system.  This  condition  fav- 
ors nitrification,  which  tends  to  exhaust  the  lime  by  the  leaching 
of  nitrate  of  lime  from  the  soil.  Such  crops  are  therefore  gen- 
erally responsive  to  applications  of  lime,  which  may  either  be 
applied  as  limestone,  burned  lime,  or  in  combination  with  phos- 
phoric acid,  as  basic  slag.  Heavy  dressings  with  farm  manure 
or  commercial  fertilizers  tend  to  drive  out  the  valuable  clovers 
and  other  leguminous  plants  and  replace  them  with  coarser 
growths.  This  is  partly  due  to  the  production  of  an  acid  soil, 
which  may  be  restored  to  normal  condition  by  applications  of 
wood  ashes  or  lime.  Yearly  applications  of  plant  food  should  be 
made  to  these  permanent  crops. 

Cereal  hays  are  made  by  cutting  the  crop  when  the  grain  is 
in  the  milk  stage  and  just  preceding  the  most  active  migration 
of  nitrogen  and  ash  constituents  to  this  part  of  the  plant.  The 
nutrient  compounds  are  then  distributed  generally  through  the 
plant  and  their  digestibility  is  less  depressed  by  cellulose  com- 
pounds than  is  the  case  at  maturity.  The  maximum  production 
of  tissue,  especially  desirable  with  these  crops,  will  be  promoted 
by  liberal  applications  of  nitrogenous  manures. 

Barley,  oats,  millet,  sorghum  and  other  cereals,  which  produce 
the  more  nutritious  straws,  are  utilized  for  hays.  They  may  be 
made  to  produce  enormous  yields,  but  at  the  expense  of  much 
plant  food.  Under  such  conditions,  they  must  be  considered  as 
particularly  exhaustive  crops  requiring  heavy  manuring. 

The  leguminous  hays,  while  comparatively  independent  of 
mammal  supplies  of  nitrogen,  are  sometimes  benefited  in  early 
stages  of  growth  by  the  application  of  soluble  forms  of  nitrogen. 
This  produces  a  plant  of  increased  vigor  and  promotes  further 


192  Agricultural  Chemistry. 

assimilation  of  food.  These  crops  feed  heavily  upon  lime,  potash 
and  phosphoric  acid.  This  fact  is  to  be  attributed  largely  to 
their  extensive  root  systems,  drawing  from  a  wide  range  of  soil 
for  a  large  production  of  dry  matter.  As  a  consequence,  these 
crops  are  especially  benefited  by  the  inorganic  constituents  of 
manures. 

The  reappearance  of  clover  in  limed  meadows  is  a  commonly 
observed  indication  of  the  value  of  this  fertilizer.  Wood  ashes 
benefit  these  crops  chiefly  by  reason  of  their  content  of  lime  and 
potash.  The  following  fertilizer  ration  per  acre  has  been  re- 
commended for  clover  and  alfalfa:  40  pounds  of  nitrate  of  soda 
or  1  ton  of  farm  manure ;  500  pounds  of  bone  meal ;  150  pounds 
of  muriate  or  sulphate  of  potash,  or  1500  pounds  of  wood  ashes; 
1  to  3  tons  of  ground  lime-stone,  as  required. 

Ensilage  is  properly  a  hay  crop.  It  is  principally  prepared 
from  corn,  although  sorghum,  millet,  clover,  cow  peas  and  other 
succulent  crops  have  been  so  treated.  The  production  of  good 
silage  depends  upon  careful  exclusion  of  the  air.  Under  this 
condition  the -mass  undergoes  changes  involving  the  consumption 
of  oxygen  and  production  of  compounds  not  previously  existing 
in  the  fresh  material.  The  temperature  of  the  mass  rises  and 
reaches  its  maximum  in  two  or  three  days.  These  changes  were  once 
thought  to  be  due  chiefly  to  organisms  producing  alcohol,  lactic 
and  acetic  acids,  and  other  products  of  fermentation.  Babcock  and 
Russell,  as  a  result  of  their  studies  on  silage,  have  concluded  that 
bacteria  are  not  the  essential  cause  of  the  changes  within  the  silo, 
but  are  probably  deleterious  and  exert  their  influence  only  in  the 
production  of  objectionable  putrefactive  changes.  These  in- 
vestigators further  conclude  that  the  changes  in  the  silo  are 
chiefly  due  to  the  respiration  of  living  plant  cells.  This  process 
either  may  involve  the  oxygen  confined  in  the  air  spaces  of  the 
ensiled  material,  in  which  case  it  is  known  as  "direct  respira- 
tion," or  it  may  utilize  only  the  oxygen  of  compounds  in  the 
plant  tissue,  this  process  being  known  as  "  intra-molecular  respir- 
ation." Both  forms  of  activity  cease  with  the  death  of  the  plant 


Crops.  193 


cells.  Hence,  the  more  mature  the  corn  when  ensiled,  the  sooner 
these  changes  and  the  losses  incident  to  them,  cease.  This  theory 
is  in  harmony  with  the  practical  experience  that  rather  mature 
corn  produces  superior  ensilage.  Maximum  yield  of  material 
and  the  production  of  good  silage  are  secured  by  selecting  the 
corn  when  in  a  glazed  state. 

Chemical  changes  in  the  silo  entail  a  loss  of  dry  matter,  the 
amount  of  which  is  dependent  upon  the  care  with  which  air  is 
excluded.  In  the  majority  of  cases  investigated  this  loss  has 
been  from  15  to  20  per  cent  of  the  dry  matter  of  the  fresh  crop 
and  in  some  cases  it  has  reached  40  per  cent.  King  states  that 
the  loss  need  not  exceed  4  to  8  per  cent  for  corn  and  10  to  18 
per  cent  for  clover.  In  64.7  tons  of  silage  packed  in  a  silo,  tight- 
ly lined  with  galvanized  iron,  he  found  an  average  loss  of  6.38 
per  cent.  The  loss  was  estimated  for  eight  separate  layers  in  the 
whole  silo  and  found  to  be  32.53  per  cent  for  the  top  layer,  23.38 
per  cent  for  the  next,  and  from  2.1  to  10.25  per  cent  for  the 
others.  The  greater  loss  for  the  more  exposed  layers  emphasizes 
the  importance  of  oxygen  in  effecting  a  loss  of  dry  matter,  and 
the  need  of  excluding  air  from  the  material  by  tightly  packing  it. 
In  properly  cured  silage  the  loss  of  dry  matter  falls  chiefly  upon 
sugars,  which  are  oxidized  to  organic  acids  and  ultimately  to 
carbon-dioxide  and  water.  A  part  of  the  protein  compounds  is 
also  altered,  with  the  production  of  amino  acids.  In  some  cases 
over  one-half  of  the  nitrogen  of  the  silage  is  present  in  the  latter 
form.  This  is  two  to  three  times  as  much  as  the  original  fodder 
contains. 

Since  the  sugars  and  proteins  are  compounds  of  high  food 
value,  the  importance  of  restricting  such  losses  in  the  silo  is  evi- 
dent. Jordan  estimates  that  a  saving  of  three-fourths  or  even 
of  one-half  the  average  losses  from  100  tons  of  corn  as  silage, 
would  increase  the  farmers'  food  resources  by  an  amount  equiv- 
alent to  from  5  to  7%  tons  of  timothy  hay. 

Root  crops  are  generally  gross  feeders  and  quite  dependent 
for  their  food  supplies  upon  readily  available  materials. 


i:»4  Agricultural  Chemistry. 

'••  The  turnip  is  a  biennial  plant  which  stores  food  the  first  season 
and  produces  seed  the  second  year.  The  several  varieties  differ 
chiefly  in  the  form  and  color  of  the  root.  The  common  turnip 
contains  about  8  per  cent  of  dry  matter,  which  is  largely  starch. 
The  rutabaga,  or  Swede  turnip,  contains  more  dry  matter  (about 
13  per  cent)  and  about  10  per  cent  of  carbohydrates.  The  lower 
content  of  water  than  in  the  turnip  promotes  better  keeping 
qualities.  Turnips  require  an  abundance  of  nitrogenous  fer- 
tilizer. Investigations  in  this  country  indicate  that  the  turnip 
family  is  less  dependent  upon  readily  available  forms  of  phos- 
phoric acid  than  other  crops. 

The  beet  is  cultivated  in  several  varieties.  It  is  a  deeper 
feeder  than  the  turnip  by  virtue  of  its  longer  tap-root.  The  com- 
mon red  beet  contains  about  the  same  proportion  of  dry  matter 
and  nutrients  as  the  rutabaga.  Mangel-wurzels,  or  field  beets, 
are  somewhat  poorer  than  the  red  beet  in  dry  matter,  and  notice- 
ably so  in  nitrogen-free  extract.  The  mangel  produces  a  large 
root  containing  about  12  per  cent  of  dry  matter.  The  sugar  beet 
is  a  smaller  variety  of  the  mangel.  It  contains  more  dry  matter 
(13  to  19  per  cent)  than  the  other  roots,  most  of  which  is  sucrose. 
The  production  of  beet  sugar  in  Europe  alone  for  1903-1904  was 
estimated  at  about  six  million  tons,  or  nearly  twice  the  world's 
production  of  cane  sugar.  These  root  crops  do  best  on  deep, 
loamy  soil,  in  rather  warm,  damp  seasons,  except  that  the  mangel 
and  sugar  beet  require  rather  dry  fall  weather.  Mangels  are 
probably  the  most  exhaustive  farm  crop  and  require  heavier  ma- 
nuring than  the  other  roots,  12  to  14  tons  of  manure  per  acre 
being  a  common  application.  They  are  less  dependent  than 
turnips  upon  phosphate  fertilizers,  but  respond  generously  to 
applications  of  nitrate  of  soda  (about  200  pounds  per  acre). 
This  crop  is  also  benefited  by  the  addition  of  common  salt.  The 
production  of  large  roots  is  sometimes  objectionable  because  the} 
contain  much  more  water  than  small  ones.  This  is  true  with 
sugar  beet,  where  a  high  production  of  sugar  is  desired. 
manuring  is  therefore  avoided  and  the  crop  is  thickly  sown. 


Crops.  195 

following  manuring  per  acre  is  recommended  for  sugar  beets: 
3  tons  of  stable  manure,  300  pounds  of  acid-phosphate,  140 
pounds  of  sulphate  of  potash.  The  soil  should  be  fairly  stocked 
with  lime. 

The  potato  is  a  surface  feeder  and  must  be  liberally  manured 
to  secure  good  yields.  This  crop  contains  20  per  cent  of  dry 
matter,  which  is  mostly  starch.  It  is  a  staple  human  food  and 
is  also  fed  to  stock.  In  Europe,  one  of  the  principal  uses  for 
the  potato  is  for  the  manufacture  of  alcohol.  Stable  manure 
appears  to  favor  growth  of  scab  and  should  be  applied  to  a  pre- 
ceding crop.  Chloride  of  potash  is  also  said  to  be  injurious  to 
this  crop.  The  fertilizer  recommended  per  acre  is :  225  pounds 
of  sulphate  of  ammonia,  500  pounds  of  acid-phosphate  and  200 
pounds  of  sulphate  of  potash. 

Fruit  crops  present  peculiar  manurial  requirements,  especially 
with  relation  to  perennial  growths.  The  composition  of  the 
20  per  cent  of  dry  matter  in  common  fruits  is  principally  of  car- 
bohydrate nature  (invert  sugar,  sucrose,  cellulose,  pentosans  and 
pectose)  with  small  amounts  of  organic  acids,  ash  and  nitrogen 
compounds.  Green  fruit  contains  starch,  which  is  converted  to 
sugar  in  the  ripening  process.  The  production  of  these  com- 
pounds creates  special  demands  for  potash.  Phosphoric  acid 
and  nitrogen  are  required  in  smaller  amounts,  except  by  the 
plum,  an  average  crop  of  which  removes  128  pounds  of  nitrogen 
per  acre.  The  strawberry,  blackberry  and  similar  fruits  will 
produce  the  best  yields  when  a  vigorous  cane  growth  is  in- 
duced by  liberal  manuring.  They  thus  respond  most  markedly  to 
applications  of  liquid  manure.  The  fruit  of  trees  draws  its  nu- 
trients from  an  extensive  woody  growth  and  volume  of  sap,  but 
these  sources  must  be  reinforced  to  keep  the  trees  in  vigorous 
bearing  condition.  Light  yearly  applications  of  farm  manure 
or  complete  fertilizers  are  recommended  for  these  crops. 

Forest  growth  presents  practically  the  same  demands  on  fer- 
tility as  do  fruit  trees,  but  as  has  been  pointed  out,  this  demand 


196  Agricultural  Chemistry. 

is  practically  covered  by  a  continuous  return  of  plant  food  from 
this  crop  to  the  soil. 

The  miscellaneous  crops,  grown  chiefly  for  the  truck  market, 
give  cash  returns  which  justify  the  expense  of  "forcing"  rations 
of  plant  food.  Such  rations  should  include  liberal  amounts  of 
nitrogen.  Tobacco  should  receive  some  nitrogen  and  a  liberal 
supply  of  potash,  with  phosphoric  acid  in  moderate  amount.  Too 
much  nitrogen  is  to  be  avoided  because  of  unfavorable  effects  on 
the  quality  of  the  tobacco  leaf.  Cotton-seed  meal  at  the  rate  of 
200  to  300  pounds  per  acre  before  planting  is  a  favorable  ration. 
Potash  should  be  applied  as  sulphate  ( 100  Ibs. ) ,  as  the  chloride 
is  injurious.  Phosphoric  acid  should  be  applied  at  the  rate  of 
200  pounds  of  acid-phosphate  or  400  pounds  of  bone  meal  per 
acre. 

Cabbages,  as  a  market  crop,  are  brought  to  harvest  early  and 
are  improved  in  quality  by  heavy  applications  of  nitrogen.  Nit- 
rate of  soda  or  sulphate  of  ammonia  at  the  rate  of  300  pounds  per 
acre  in  two  or  three  top  dressings  is  recommended  in  addition 
to  general  manuring. 

No  specific  rules  can  be  laid  down  for  the  application  of  fer- 
tilizers to  each  crop,  because  of  the  greatly  variant  conditions  of 
soil  and  climate  under  which  it  must  be  grown.  These  factors, 
particularly  the  latter,  exert  a  profound  influence  on  the  growth 
of  plants.  Each  farmer  must  determine  the  requirements  of  his 
own  conditions  by  the  fertilizer  tests  described  in  the  chapter 
on  "Fertilizers." 

Factors  influencing  the  composition  of  the  crop  are:  Stage 
of  growth,  exposure  at  harvest,  fertilizers  and  environment. 

The  stage  of  growth  has  been  shown  to  present  marked  differ- 
ences in  the  feeding  value  of  the  straw  of  cereal  plants.  In  the 
true  hay  crops  the  grain  takes  up  most  of  the  nutrients  of  the 
plant  during  the  ripening  period.  This  results  in  increased  fil 
content  and  decreased  feeding  value  of  the  stems.  The  Conn* 
ticut  Experiment  Station  gives  the  following  composition 
timothy  at  successive  periods  preceding  ripening. 


Crops. 


197 


Composition  of  Dry  Matter  of  Timothy. 


Stage  of  growth 

Ash 

Crude 
protein 

Crude 
fiber 

Nitrogen 
free 
extract 

Ether 
extract 

Well  headed  out  .... 
In  full  blossom  

Per  cent 
4.7 
4  3 

Per  cent 
9.6 
7.1 

Per  cent 
33.0 
33  3 

Per  cent 

50.8 
53.3 

Per  cent 
1.9 
2  0 

When  out  of  blo.-som 
Nearly  ripe  

4.1 
3.0 

7.1 

6.8 

33.8 
35.4 

53.3 
52.2 

1.7 
2.0 

It  will  be  observed  that  the  protein  and  ash  of  the  hay  decrease 
rapidly  from  the  heading  out  stage,  while  the  fiber  increases  at 
the  later  stages.  The  nitrogen-free  extract  at  the  later  stages  is 
probably  less  valuable  than  at  the  earlier  periods  of  growth  as 
a  result  of  increased  proportions  of  indigestible  pentosans  and 
similar  compounds.  Thus,  while  the  hay  crops  increase  in  the 
quantity  of  dry  matter  to  the  end  of  the  ripening  period,  they 
decrease  in  palatability  and  food  value  when  harvesting  is  de- 
layed too  long.  These  conditions  are  more  serious  with  legume 
hays,  where  a  large  percentage  of  protein  is  involved.  This  is 
shown  in  the  following  table  on  the  composition  of  alfalfa  hay 
published  by  the  Kansas  Experiment  Station : 

Composition  of  Dry  Matter  of  Alfalfa  Hay. 


Ash 

i                   | 

Crude 
protein 

Crude 
fiber 

Nitrogen 
free 
extract 

Ether 
extract 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

First  stage  (about  10 

per  cent  in  bloom) 

10.45 

18.50 

32.20 

27.29 

1.56 

Second  stage  (about 

%    per    cent     in 

bloom)  

10.28     i       17.21 

35.37 

34.00 

1.05 

Third     stage      (full 

bloom)  

8.45 

14.43 

36.10 

39.  G2 

.    1.41 

19S 


Agricultural  Chemistry. 


The  decrease  in  protein  at  the  last  stage  is  marked.  These 
data  indicate  that  the  most  favorable  mean  between  quantity  and 
quality  of  crop  will  be  secured  by  cutting  grasses  and  clovers 
between  early  and  full  bloom. 

With  corn,  conditions  are  different.  Analyses  at  the  Maine 
Experiment  Station  gave  the  following  data: 

Composition  of  Dry  Matter  of  Corn  Plant. 


Stage  of  growth 

Ash 

Crude 
protein 

Crude 
fiber 

Sugar 

Starch 

Nitro- 
gen 
free 
extract 

Ether 
extract 

Very  immature 
(Aug.  15)   

Per 

cent 

9  3 

Per  cent 
15.0 

Per 

cent 

26.5 

Per 

cent 

11.7 

Percent 

Percent 
46.6 

Per  cent 
2.6 

A  few  roasting  ears 
(Aug.  28)  
All  roasting  stage 
(Sept.  4)  

6.5 
6  ? 

11.7 
11.4 

23.3 
19.7 

20.4 
20.6 

2.1 
4.9 

55.6 
59.7 

2.9 

3.0 

Some  ears  glazing 
(Sept.  12)  
All  ears  glazed 
(Sept  21) 

5.6 
5  Q 

9.6 
9.2 

19.3 
18  6 

21.1 
16.5 

5.3 
15  4 

62.5 
63  3 

3.0 
3.0 

The  material  increase  in  starch  and  other  digestible  carbo- 
hydrates more  than  offsets  the  relative  decrease  in  crude  protein 
and  is  accompanied  moreover  by  a  decrease  of  crude  fiber.  Feed- 
ing experiments  moreover  have  shown  that  mature  corn  is  more 
digestible  than  the  immature  plant,  both  as  fodder  and  as  silage. 

Exposure  to  the  weather,  particularly  undue  exposure  to 
rainy  weather,  detracts  from  the  value  of  the  crop.  This  is  duo 
to  the  leaching  away  of  nutrient  compounds  by  the  rain. 

The  following  table  from  Bulletin  135  of  the  Kansas  Station 
shows  the  extent  of  such  losses  from  alfalfa  hay,  assuming,  as  is 
approximately  true,  that  no  fiber  is  lost.  The  hay  was  exposed 
during  15  days,  during  which  time  it  was  subjected  to  three 
rains  amounting  to  1.76  inches: — 


Crops. 

Louses  by  Rain  to  100  Pounds  of  Alfalfa  Hay. 


199 


Crude 
Ash 

Crude 
protein 

Crude 
fiber 

Nitro- 
gen 
free 
extract 

Crude 
fat 

Total 

Pounds  in  original           ...    . 

12  2 

18  7 

26.5 

38.7 

3.9 

100.0 

Pounds  in  damaged  .       

S.7 

7.5 

26.5 

23.0 

2.6 

68.3 

Pounds  lost  

3  5 

11.2 

00.0 

15  7 

1.3 

31.7 

Per  cent  lost  

28.7 

60  0 

00.0 

41.0 

33.3 

31.7 

Not  only  has  nearly  one-third  of  the  total  dry  matter  been  lost, 
but  over  one-third  of  this  loss  has  fallen  upon  protein,  which  is 
the  most  valuable  constituent  of  the  hay.  For  every  pound  of 
protein  in  the  damaged  hay,  one  and  one-half  pounds  have  been 
lost  by  exposure. 

Curing  processes  may  seriously  affect  the  composition  of 
crops.  Alfalfa  hay  furnishes  a  striking  example  of  this  fact. 
When  cut  early,  this  crop  bears  73  pounds  of  leaf  for  100  pounds 
of  stem.  The  leaf,  however,  is  much  richer  in  nutrients  than 
the  stem.  Thus,  for  100  pounds  of  each  constituent  in  the  stems, 
the  leaves  of  an  equivalent  amount  of  crop  in  each  case  will 
contain  of:  fat,  450  pounds;  protein,  250  pounds;  nitrogen  free 
extract,  135  pounds;  crude  fiber,  28  pounds.  That  portion  of 
the  crop  especially  subject  to  mechanical  loss  in  hay  making  is 
therefore  the  most  valuable  as  fodder. 

Headden  has  estimated  the  mechanical  loss  of  alfalfa  in  har- 
vesting at  15  to  20  per  cent  of  the  dry  crop.  In  extreme  cases 
60  per  cent  or  more  may  be  left  on  the  field.  This  loss  falls 
chiefly  upon  the  leafy  tissue.  More  valuable  hay  will  be  secured 
if  the  crop  is  cut  between  early  and  full  bloom  and  handled  to 
a  minimum  extent,  than  if  it  is  allowed  to  become  brittle  by  aging 
or  over-curing  at  harvest  and  then  excessively  handled. 

Fertilizers  influence  the  'composition  of  the  crop  to  a  limited 
extent,  both  by  their  amount  and  their  nature.  This  effect  has 
been  observed  principally  with  reference  to  the  increase  of  pro- 


200  Agricultural  Chemistry. 

tern  formation  by  application  of  nitrogenous  fertilizers.  Pingree 
found  that  nitrogen  applied  to  oats,  in  the  form  of  dried  blood, 
slightly  increased  the  protein  content  of  both  grain  and  straw. 
At  the  Storrs  (Conn.)  Experiment  Station,  corn,  oats  and  mixed 
grass  (timothy,  red  top  and  Kentucky  blue  grass)  were  supplied 
with  gradually  increasing  amounts  of  nitrogen,  added  to  a  uni- 
form ration  of  potash  and  phosphoric  acid.  "Within  certain 
limits,  the  protein  content  of  the  corn  and  oat  grains,  oat  straw, 
corn  stover  and  grasses  was  increased,  somewhat  in  proportion 
to  the  amounts  of  nitrogen  supplied.  Parozzani  found  that  in- 
creased application  of  super-phosphates  to  corn  resulted  in  a 
corresponding  increase  of  total  phosphoric  acid  in  the  seed.  In- 
vestigation of  the  distribution  of  phosphorus  in  the  seed  showed 
that,  while  the  amount  in  nuclein  compounds  remained  constant, 
the  amounts  in  the  forms  of  lecithin  and  phytin  were  increased. 
Total  nitrogen  in  the  seed  was  not  sensibly  affected,  but  the  pro- 
portion of  true  protein  compounds  was  slightly  increased  and 
this  increase  was  limited  to  a  specific  protein,  namely,  zein. 

Such  examples  as  these  are  limited.  From  an  intimate  knowl- 
edge of  the  long  series  of  fertilizing  experiments  at  Rothamsted, 
Hall  is  led  to  state  that,  ''Although  the  composition  and  quality 
of  the  grain  is  affected  by  the  amount  of  nitrogen  supplied  to  the 
crop,  it  is  really  astonishing  to  find  how  small  are  the  changes 
brought  about  by  extreme  differences  in  manuring. ' '  The  effects 
may  be  more  marked  with  other  parts  of  the  crop,  but,  quoting 
Hall  further:  "The  crop  reacts  against  variations  in  the  com- 
position of  the  soil  and  tends  to  keep  its  own  composition  con- 
stant. When  also  the  time  comes  for  the  grain  to  be  formed  - 
from  the  reserve  materials  already  stored  up  in  the  plant,  an- 
other attempt  is  made  to  turn  out  a  standard  product.  Even  on 
the  Rothamsted  plots,  where  the  differences  in  the  supply  of 
nutrients  are  extreme  and  have  been  accumulating  for  50  years, 
the  composition  of  the  grain  changes  more  from  one  season  to 
another  than  it  does  in  passing  from  plot  to  plot." 

Environment  has  been  found  to  influence  the  composition 


•• 


Crops.  201 

the  crop  more  than  any  other  factor.  The  sugar  beet  has  given 
valuable  results  along  this  line  in  experiments,  conducted  by 
Wiley  in  this  country  from  1900  to  1905.  Beets  were  grown 
from  the  same  seed  at  12  experiment  stations  scattered  from 
Kentucky  to  Wisconsin  and  from  New  York  to  California.  At 
Utah,  California  and  Colorado  the  crops  were  grown  under  ir- 
rigation. Chemical  and  meteorological  records  were  carefully 
kept  in  all  cases.  As  a  result  of  this  and  similar  investigations, 
Wiley  concludes  that  the  soil  and  fertilizers  have  only  a  limited 
influence  and  that  temperature  (or  latitude)  is  the  most  potent 
element  of  the  environment  in  the  production  of  a  beet  rich  in 
sugar.  Excessive  rain  fall  and  irrigation  affect  the  beet  only  in- 
cidentally by  increasing  the  yield  with  a  proportionate  reduction 
in  percentage  of  sugar,  and  dry  tillage  produces  opposite  effects. 
With  these  conclusions  as  a  basis,  there  has  been  mapped  for  the 
northern  United  States  a  belt  of  country  which  presents  optimun 
climatic  conditions  for  the  production  of  sugar  beets. 

Wheat  has  been  tested  in  a  similar  manner  and  the  results 
have  been  reported  recently  by  Le  Clerc.  Crops  were  grown 
from  the  same  seed  at  the  apices  of  two  great  triangles ;  namely : 
Kansas,  South  Dakota  and  California;  and  Kansas,  Texas  and 
California.  The  results  demonstrate  that  the  same  variety  of 
wheat  brought  from  different  localities  and  grown  side  by  side  in 
one  locality,  yields  crops  of  almost  the  same  appearance  and  com- 
position. On  the. other  hand,  "wheat  of  any  one  variety  from 
any  one  source  and  absolutely  alike  in  chemical  and  physical 
characteristics,  when  grown  in  different  localities,  possessing  dif- 
ferent climatic  conditions,  yields  crops  of  very  widely  different 
appearance  and  very  different  chemical  composition."  Thus, 
with  relation  to  protein,  the  constituent  of  most  concern,  the 
seed  of  Kubanka  wheat  grown  in  South  Dakota  in  1905  contained 
13.03  per  cent.  The  1906  crop  grown  from  this  seed  contained : 
in  Kansas,  19.85  per  cent  of  protein  in  the  seed,  in  California, 
9.68  per  cent,  and  in  South  Dakota,  14.24  per  cent.  The  seed 
from  these  localities  grown  in  1907  at  California  contained  9.70, 


202  Agricultural  Chemistry. 

9.90  and  9.05  per  cent  of  protein  in  the  seed,  respectively,  while 
portions  of  the  same  seeds  grown  in  South  Dakota  contained 
14.24,  13.89  and  12.87  per  cent  of  protein.  The  same  condition 
obtained  with  Crimean  wheat  grown  in  the  other  triangle,  Kansas 
uniformly  producing  the  highest  protein  content  in  the  grain 
and  California  the  lowest.  These  results  lead  to  the  conclusion 
that  a  crop  should  be  improved  by  selection  in  the  region  where 
it  is  to  be  grown,  or  that  "seed  should  be  selected  from  a  region 
of  similar  climatic  condition. ' ' 

The  author  just  quoted  compared  eight  samples  of  Durum 
wheat  grown  in  arid  and  semi-arid  regions  with  seven  samples 
of  the  same  variety  from  humid  regions.  The  seed  from  dry 
regions  contained  17.23  per  cent  of  protein,  and  that  from  humid 
regions,  13.75  per  cent ;  and  the  samples  weighed  30.3  grams  and 
33.5  grams  per  1000  grains,  respectively.  Abundant  water  sup- 
ply is  thus  productive  of  plump,  starchy  grains,  while  dry  con- 
ditions produce  a  smaller  grain  richer  in  protein.  This  contrast 
is  illustrated  by  the  change  in  composition  of  Durum  wheat 
grown  in  Mexico.  The  original  seed  contained  12.3  per  cent  pro- 
tein. Grown  under  irrigation  it  produced  seed  of  11.1  per  cent 
protein,  non-irrigated,  17.7  per  cent.  Shutt  has  confirmed  these 
data  with  wheat  grown  on  irrigated  and  non-irrigated  soil  at 
Manitoba,  Canada.  Lawes  and  Gilbert  had  previously  observed 
at  Kotharnsted  that  hot,  moderately  dry  seasons  produced  the 
best  quality  of  wheat. 

Sweet  corn  has  been  similarly  tested  by  Wiley  for  several  suc- 
cessive years.  The  results  have  shown  that  the  content  of  sugar 
is  less  influenced  by  temperature  than  in  the  case  of  the  sugar 
beet.  The  ripening  crop  was  followed  along  the  Atlantic  coast 
from  Florida  to  Maine.  Contrary  to  the  results  with  the  sugar 
beet  the  higher  average  content  of  sugar  appeared  to  be  found 
in  the  warmer  climates.  The  lower  temperatures  of  the  North, 
however,  retard  the  ripening  process  and  render  the  corn  suc- 
culent for  a  longer  period  than  does  the  warm  climate  of  the 
extreme  South.  "Wiley  concludes  that  the  amount  and  distribu- 


Crops.  203 

tion  of  rainfall  is  the  most  important  factor  affecting  the  edible 
quality  of  green  sweet  corn,  and  that  the  favorable  effects  of 
moderate,  well  distributed  rain-fall  indicate  that  the  northern 
states  will  continue  to  produce  the  best  crop  outside  the  irrigated 
districts.  But  no  special  area  for  sweet-corn  growing  can  be 
mapped  as  has  been  done  in  the  case  of  the  sugar  beet. 

Crop  rotation  should  be  rationally  based  upon  the  varying  de- 
mands of  crops  for  plant  food  and  the  characteristic  feeding 
habits  of  individual  species  of  plants.  When  the  plant  food  of 
the  surface  soil  has  been  exhausted  by  such  shallow  rooted  crops 
as  corn,  grasses  and  turnips,  they  should  be  followed  by  deep 
rooted  crops,  such  as  wheat,  mangels,  or  alfalfa.  Not  only  will 
the  latter  crops  obtain  their  supplies  of  food  from  the  lower 
layers  of  the  soil,  but  they  leave  a  portion  of  it  at  the  surface 
in  roots  and  stubble,  from  which  it  becomes  available  to  succeed- 
ing crops.  No  more  striking  example  of  this  fact  is  furnished 
than  that  of  alfalfa.  According  to  Headden,  the  roots  and  stub- 
ble of  alfalfa  to  a  depth  of  6%  inches  contain  approximately 
2.86  tons  of  dry  matter  per  acre,  having  the  following  constit- 
uents :  total  ash  172  pounds ;  phosphoric  acid  24  pounds ;  sulphur 
trioxide  9  pounds ;  lime  50.5  pounds ;  chlorine  6.5  pounds ;  mag- 
nesia 35.15  pounds;  potash  44.5  pounds;  and  104  pounds  of  ni- 
trogen. Reference  to  the  table  in  the  Appendix  which  gives 
"Plant  food  removed  by  crops,"  shows  that  the  stubble  of  al- 
falfa alone,  places  in  the  surface  soil  as  much  plant  food  as  is 
removed  by  total  cereal  crops. 

The  waste  tops  of  the  mangel  crop  can  also  restore  to  the 
soil  as  much  food  as  is  required  by  an  average  grain  crop.  Not 
only  will  these  crops  restore  fertility  to  the  surface  soil,  but  their 
deep  root  systems,  and  the  deep  thorough  tillage  demanded  by 
them,  will  benefit  the  physical  condition  of  the  soil  when  they 
are  grown  in  rotations. 

Increase  of  soil  nitrogen  is  the  most  valuable  effect  produced 
by  legume  crops  grown  in  systems  of  rotation.  In  this  connec- 
tion the  work  of  Shutt  in  Saskatchewan,  Canada,  is  of  interest. 


204 


Agricultural  Chemistry. 


lie  compared  a  virgin  soil  of  that  province  with  one  that  had 
been  continuously  cultivated  to  cereal  grains  or  fallow  for  20 
years.  The  cultivated  soil  contained  0.253  per  cent  of  nitrogen 
(to  a  depth  of  8  inches)  and  the  virgin  soil  contained  0.371  per 
cent.  This  difference  represented  a  loss  of  2200  pounds  of  nitro- 
gen per  acre  by  the  system  of  cultivation  practiced.  Investi- 
gating the  possibility  of  restoring  nitrogen  to  the  soil,  Shutt  grew 
common  red  clover  upon  a  poor  sandy  soil,  cutting  the  crop  twice 
yearly  and  leaving  it  upon  the  soil.  At  the  end  of  each  second 
season  the  crop  was  turned  in  and  the  plot  re-sown  the  next 
spring.  In  five  years  of  this  treatment  the  soil  gained  over  300 
pounds  of  nitrogen  per  acre  to  a  depth  of  four  inches,  despite 
inevitable  losses  by  nitrification  and  leaching. 

The  effect  of  the  growth  of  clover  on  succeeding  crops  was 
demonstrated  by  Shutt  in  field  experiments.  Two  series  of  plots 
were  used,  on  one  of  which  clover  was  compared  with  wheat, 
while  on  the  other  oats  and  clover  were  compared  with  oate. 
The  first  series  will  be  described.  On  one  plot,  clover  was  sown 
alone  and  one  cutting  made  and  removed.  The  crop  was  turned 
under  in  the  following  spring.  On  the  other  plot,  wheat  was 
grown  and  harvested  as  usual.  The  effect  of  this  treatment  was 
observed  on  grain  and  root  crops  for  three  succeeding  years,  with 
the  following  resultant  data: — 

Increase  of  Crop  Due  to  Growth  of  Clover. 


1900 

1901 

1902 

1903 

Tons 

Lbs. 

Bush. 

Lbs. 

Tons 

Lbs. 

Plot  A:  Clover  

Corn 

27 

1,760 

Oats 

75 

10 

Sugar 
beets 

22 

HOO 

PlotB:  Wheat  

Corn 

19 

1,280 

Oats 

51 

26 

«< 

8 

1  ,  2(>0 

I  ncrease  due  to  clover 

Corn 

8 

480 

Oats 

23 

18 

<  i 

13 

1,:;40 

Crops. 


205 


This  effect  was  obtained  without  a  sacrifice  of  the  crop  and 
must  have  been  chiefly  due  to  the  nitrogen  supplied  by  the  stub- 
ble and  second  growth  of  the  clover. 

The  distribution  of  nitrogen  in  the  legume  crop  bears  an  im- 
portant relation  to  its  proper  use  in  rotations.  Shutt  gives  the 
distribution  of  nitrogen  between  the  roots  and  stubble  and  the 
tops  of  legumes  as  follows: — 


Nitrogen  in  Legumes. 

Legumes:  One  season's  growth 

Nitrogen  in  parts  of  crop 
(Pounds  per  acre  of  crop} 

In  tops 

In  9  in.  depth  of 
root  and  stubble 

Clover,  common  red 

90 
82 
85 
75 
129 
82 
63 
119 

48 
48 
19 
61 
18 
13 
15 
10 

Clover,  mammoth 

Clover,  crimson                            

Alfalfa  . 

Hairy  Vetch 

Sov  bean  . 

Horse  bean 

Pea 

The  proportion  of  the  total  nitrogen  of  the  crop  contained  in 
the  roots  of  common  red  and  mammoth  clovers  and  alfalfa  in- 
dicate the  effectiveness  of  the  residues  of  these  crops  as  sources 
of  nitrogen,  when  they  are  grown  in  rotations  and  the  crop 
harvested.  The  figures  for  alfalfa  are  probably  much  below  the 
average  and  fail  to  do  justice  to  the  crop.  The  condition  is  dif- 
ferent with  shallow  rooted  legumes.  Thus,  with  the  vetch  and 
pea,  a  large  supply  of  nitrogen  in  the  tops  is  correlated  with  a 
comparatively  small  amount  in  the  roots.  Marked  benefit  from 
these  crops  in  rotations  can  be  secured  only  where  the  whole 
growth  is  turned  in.  Snyder  states  that  the  nitrogen  content 
of  the  soil  can  be  maintained  and  even  slightly  increased  when 
clover  is  grown  two  years  in  a  five  course  rotation  with  grains 
and  timothy  to  which  farm  manures  are  applied. 


CHAPTER  IX 
THE  ANIMAL  BODY. 

The  elements  found  in  animal  tissue  are  the  same  as  those 
found  in  the  plant  world,  and  while  sodium  and  chlorine  are  con- 
sidered by  some  as  non-essential  for  plant  development,  in  the 
formation  of  the  animal's  tissue  they  are  indispensable.  Fluor- 
ine and  silicon  are  also  always  found  in  the  animal  body,  but 
are  not  known  to  be  absolutely  essential  for  life  or  growth. 
Fluorine  occurs  in  small  quantities  in  the  teeth  and  bones,  and 
silicon  in  the  hair,  wool  and  feathers. 

The  compounds  forming  the  animal  body  are  many  and  very 
complex  and  only  a  brief  survey  of  the  principal  ones  can  be 
given  here. 

The  constituents  of  the  animal  body  may  be  divided  into: — 

(1)  Inorganic  compounds,  including  water,  various  acids  and 
numerous  salts ;  some  are  in  the  solid  state,  as  the  calcium  phos- 
phate of  the  bone  Bothers  are  in  solution  as  the  sodium  chloride 
of  the  blood. 
(2)   Organic  compounds, 


Simple-proteins, 
amino-acids,  etc. 

Conjugated-proteins 

Derived 
proteins 

(a)  Nitrogenous  

Albumins 

Nucleo-proteins 

Proteoses 

Globulins 
Albuminoids 
Amino-acids 
Amides 

Phosp  ho  -proteins 
Glyco-proteins 

Peptones 

(l>)  Non  -nitrogenous.  .  . 

Fats 
Carbohydrates 

Of  the  inorganic  constituents,  by  far  the  largest  part  is  con- 
tained in  the  bones.     In  fat  animals  75  to  85  per  cent  of  the 
ash  constituents  of  the  body  are  found  in  the  bones.     Bono 


The  Animal  Body.  207 

ash  consists  of  phosphate  of  calcium,  with  a  small  quantity  of 
carbonate  of  calcium  and  phosphate  of  magnesium.  In  muscle 
by  far  the  most  abundant  ash  constituent  is  phosphate  of  potas- 
sium. Potassium  salts  are  also  abundant  in  the  "yolk"  of  un- 
washed wool  and  in  the  sweat  of  horses  and  other  animals.  Blood, 
on  the  other  hand,  always  contains  a  preponderance  of  sodium 
salts. 

The  nitrogenous  substances  constituting  the  animal  body  are 
extremely  varied  in  character  and  properties  and  it  would  be 
impossible  in  a  book  of  this  kind  to  attempt  to  describe  them  in 
detail.  The  albumins  and  globulins  form  the  substance  of  ani- 
mal muscle  and  nerve,  and  the  greater  part  of  the  solid  matter 
of  blood.  They  are  undoubtedly  of  the  greatest  importance  in 
the  animal  economy.  The  albuminoids  form  the  substance  of 
skin  and  sinew,  of  all  connective  tissue,  and  also  the  protein 
material  of  cartilage  and  bone.  Keratin,  the  principal  protein 
of  horn,  hair,  wool  and  feathers,  belongs  to  this  class.  The  re- 
markable difference  in  the  properties  of  the  protein,  keratin,  and 
the  protein,  serum-albumin,  lies  in  the  internal  structure  of  their 
respective  molecules. 

The  nucleo-proteins  always  contain  phosphorus  and  are  con- 
tained in  every  cell.  They  are  of  special  importance  in  all  life 
processes.  The  phospho-proteins  are  represented  in  the  animal 
kingdom  by  the  important  nitrogenous  body  found  in  milk, 
namely,  casein.  This  class  of  bodies  is  also  represented  in  the 
yolk  of  the  egg,  in  the  form  of  the  protein,  vitellin.  These  phos- 
pho-proteins contain  phosphorus  just  as  the  nucleo-proteins  do, 
but  differ  in  their  internal  structure  from  those  bodies.  The 
glyco-proteins  are  compounds  of  a  protein  molecule  with  a  sub- 
stance, or  substances,  containing  a  carbohydrate  group.  In 
solution,  they  are  characterized  by  being  ropy  and  mucilaginous 
and  are  contained  in  the  mucus  secretions  of  many  membranes 
and  glands  of  the  animal. 

The  proteoses  and  peptones  are  found  in  the  digestive  tract  of 
the  animal  and  are  derived  from  the  proteins  of  the  food  by  the 


208  Agricultural  Chemistry. 

action  of  the  proteolytic  enzymes  of  the  alimentary  canal.  They 
niv  water-soluble  bodies. 

All  of  these  protein  bodies  contain  very  similar  amounts  of 
nitrogen — namely,  15  to  18  per  cent.  Besides  the  above  nitro- 
genous materials  constituting  tissue,  the  animal  juices  contain  a 
variety  of  nitrogenous  substances  such  as  creatin,  creatinin,  sar- 
cosine,  etc.,  but  with  which  we  are  not  concerned. 

The  amino-acids  are  simple  nitrogenous  bodies  formed  during 
the  process  of  digestion  from  the  proteins  of  the  food  and  are 
believed  to  be  the  building  materials  out  of  which  the  animal 
reconstructs  its  own  tissue  protein. 

The  amides,  principally  represented  by  urea  in  the  urine,  are 
the  simple  nitrogenous  waste  products  of  the  tissues.  In  the 
cow,  85  to  95  per  cent  of  the  total  nitrogen  in  the  urine  is  in  this 
form. 

The  fats  occurring  in  the  animal  body  are  principally  stearin, 
palmitin  and  olein.  Stearin  predominates  in  hard  fats  and  olein 
in  more  fluid  fats.  They  are  identical  in  composition  with  these 
same  materials  described  in  the  chapter  on  the  plant.  Lecithin, 
a  complex  fat  containing  both  nitrogen  and  phosphorus,  is  also 
widely  distributed  in  animal  tissue. 

Carbohydrates.  The  important  carbohydrate  of  the  animal 
body  is  glycogen.  found  in  considerable  quantities  in  the  liver 
and  in  smaller  amounts  in  the  muscular  tissue.  It  resembles 
starch  in  its  constitution.  At  no  time  does  it  constitute  an  ap- 
preciable proportion  of  the  animal's  weight.  In  this  respect 
animals  differ  from  plants.  In  the  latter  the  stored  reserve  ma- 
terial is  usually  starch,  while  in  the  animal,  fat  is  the  reserve 
material.  The  glycogen  found  in  animal  tissue  has  had  its  origin 
from  the  various  carbohydrates  of  the  feed.  These  have  been 
absorbed  from  the  digestive  tract  largely  in  the  form  of  dextrose, 
one  of  the  simpler  sugars,  and  from  which  glycogen  has  been 
rebuilt. 

Composition  of  farm  animals.  The  amounts  of  water,  nitro- 
genous matter,  fat  and  ash  constituents  present  in  a  large  num- 


The  Animal  Body. 


209 


her  of  animals,  have  been  determined  by  Lawes  and  Gilbert  at 
the  Rothamsted  Station.  The  following  table  shows  the  per- 
centage composition  of  the  whole  bodies  of  various  farm  animals. 
The  fat  pig  was  one  grown  for  fresh  pork,  not  for  bacon.  Store 
animals  are  those  in  good  flesh,  but  not  fat. 

Composition  of  Farm  Animals. 


Animal 

Water 

Fat 

Protein 

Ash 

Content  of 
stomach, 
etc. 

Fat  calf  

Per  cent 
63.0 

Per  cent 
14.8 

Per  cent 
15.2 

Per  cent 
3  8 

Per  cent 
3  2 

Half  fat  ox         .... 

51.5 

19.1 

16.6 

4  6 

8  2 

Fat  ox  

45.5 

30.1 

14  5 

3  9 

6  0 

Fat  lamb  

47.8 

28.5 

12.3 

2  9 

8  5 

Store  sheep  

57.3 

18.7 

14.8 

3  2 

6  0 

Half  fat  sheep  

50.2 

23.5 

14  0 

3.2 

9  1 

Fat  sheep  

43.4 

35.6 

12.2 

2  8 

6  0 

Store  pig  

55.1 

23.3 

13  7 

2.7 

5  2 

Fat  pier  .  . 

41.3 

42.2 

10  9 

1.6 

4  0 

It  will  be  noticed  that  in  nearly  every  case  water  is  the  largest 
ingredient  of  the  animal  body.  The  proportion  of  water  is  great- 
est in  young  and  lean  animals  and  diminishes  toward  maturity 
and  especially  during  fattening.  The  proportion  of  nitrogenous 
matter  and  ash  tends  to  increase  as  the  animal  ages,  but  dimin- 
ishes during  fattening.  The  half  fat  ox  contains  6  per  cent  more 
water  than  the  fat;  the  store  sheep  14  per  cent  more  than  the 
extra  fat,  and  the  store  pig  14  per  cent  more  than  the  fat.  The 
fattening  process  does  not  involve  a  replacement  of  the  water 
already  in  the  tissues,  but  the  increase  is  much  more  largely  dry 
matter.  Because  this  increase  during  fattening  is  largely  fat, 
the  proportion  of  protein  and  ash  in  the  dry  substance  of  the 
fattened  animal  has  decreased  relatively. 

The  largest  proportion  of  nitrogenous  matter  a*nd  ash  are 
found  in  the  ox,  the  smallest  in  the  pig.  The  difference  in  the 
proportion  of  ash  is  chiefly  due  to  the  wide  difference  in  the 


210 


Agricultural  Chemistry. 


proportion  of  bone  in  these  two  animals.  Fat  is  found  in  great- 
est quantity  in  the  pig  and  is  least  in  the  ox. 

The  following  table  shows  the  quantity  of  nitrogen  and  the 
principal  ash  constituents  in  the  fasted  live  weight  of  the  animals 
analyzed  at  Rothamsted.  The  table  is  based  upon  a  weight  of 
1000  pounds  for  each  animal.  The  table  also  includes  milk,  wool 
and  eggs,  and  supplies  information  as  to  the  loss  a  farm  would 
sustain  by  the  sale  of  animal  products.  According  to  this  table, 
the  ox  contains,  in  proportion  to  its  weight,  a  larger  amount  of 
nitrogen  and  a  much  larger  amount  of  lime  and  phosphoric  acid 
than  either  the  sheep  or  pig.  Of  all  the  animals  raised  on  the 
farm,  the  pig  contains  the  least  of  all  the  important  ash  con- 
stituents. 

Attention  should  be  called  to  the  large  amount  of  potash  in 
unwashed  wool.  It  is  possible  for  the  fleece  to  contain  more 
potash  than  the  whole  body  of  the  shorn  sheep.  The  fleeces  of 
four  Hampshire  Down  sheep,  analyzed  at  Rothamsted,  contained 
about  6.5  per  cent  of  nitrogen  and  2  to  3  per  cent  of  ash. 


Ash  Constituents  and  Nitrogen  in  1000  Pounds  of  Various  Animah  and 
the  Same  Weight  of  Their  Products. 


Animal 

Nitrogen 

Phos- 
phoric 
acid 

Potash 

Lime 

Magnesia 

Fat  calf. 

Lbs. 
24  6 

Lbs. 

TS  Q 

Lbs. 

o  n 

Lbs. 

1ft  4 

Lbs. 

00 

Half  tat  ox. 

27  4 

18  3 

9    Q 

91    1 

A     Q 

Fat  ox.  .  . 

23  2 

15  5 

1    7 

i  7  q 

Of! 

Fat  lamb.. 

19  7 

11  2 

i    fi 

19     Q 

0     ^ 

Store  sheep  
Fat  sheep. 

23.7 

19  7 

11.8 
10  4 

1  .7 
1   5 

13.2 

I  1      Q 

0.5 
0  5 

Store  pig.  .  . 

22  0 

10  6 

1    Q 

10  8 

0  f\ 

Fat   pig  

17  fi 

6  5 

1  4 

fi  3 

0  3 

Wool  (unwashed).  . 
Wool   (  waebdH)  .  .  .  . 
Milk... 

54.0 
94.4 

5  7 

0.7 
1.8 
2  0 

56.2 
1.9 

1    7 

1.8 
2.4 

1    7 

0.4 
0.6 

M      •> 

Hen's  eggs 

20  0 

4  *> 

1    7 

fiO  X 

1    0 

The  Animal  Body. 


211 


Fattening  an  animal  increases  the  proportion  of  butcher's 
meat  while  at  the  same  time  it  materially  modifies  its  composition. 
Jordan  gives  the  proportion  of  dressed  carcass  in  per  cent  as 
follows : 

Ox  Sheep  Swine 

Lean  animal 47  45  73 

Fat  animal 60  53  82 

The  composition  of  the  increase  of  an  animal  varies  much  un- 
der different  circumstances.  The  increase  of  a  young  growing 
animal  will  contain  much  water,  protein  and  ash ;  that  of  a  ma- 
ture fattening  animal  will  consist  chiefly  of  fat.  From  this  it 
follows  that  a  larger  proportion  of  protein  and  ash  is  needed 
luring  the  earlier  periods  of  growth ;  but,  because  of  the  larger 
proportion  of  water,  a  smaller  amount  of  food  is  required  to 
produce  one  pound  of  gain. 

The  composition  of  the  increase  of  oxen,  sheep  and  pigs,  when 
passing  from  the  " store"  to  the  "fat"  condition  has  been  cal- 
culated by  Lawes  and  Gilbert. 

Percentage  Composition  of  the  Increase  While  Fattening. 


Water 

Protein 

Fat 

Ash 

Sheep  .  . 

Per  cent 
22  0 

Per  cent 

7  2 

Per  cent 
68  8 

Per  cent 
2  0 

i      ^ 
jxen  

24  6 

7.7 

66  2 

1  5 

Pigs 

9g  6 

7  8 

63  1 

0  5 

Average  

25.1 

7.6 

66  0 

1  3 

The  increase  during  the  fattening  stage  of  growth  is  seen  to 
Britain  8  to  9  parts  of  fat  for  one  of  nitrogenous  matter. 

Important  parts  of  the  animal  body.  Blood  consists  of  a 
;.io  lor  less  liquid — plasma — holding  in  suspension  numerous  small 
polid  bodies,  the  red  and  white  corpuscles.  The  red  corpuscles 
|give  the  blood  its  characteristic  color.  These  corpuscles  have  a 
Definite  structure  and  make  up  30  to  40  per  cent  of  the  blood. 


212  Agricultural  Chemistry. 

When  taken  from  an  animal  the  plasma  quickly  deposits  one  of 
its  protein  constituents,  fibrin,  which,  entangling  the  corpuscles, 
causes  them  to  separate  as  a  clot  from  the  yellowish  liquid — the 
serum.  Blood  plasma  is  therefore  the  liquid  portion  of  fresh 
blood,  while  blood  serum  is  the  liquid  portion  after  clotting.  The 
latter  differs  from  the  former  by  having  lost  its  fibrin  and  a 
portion  of  its  lime,  magnesia  and  phosphoric  acid. 

Blood  is  the  nutrient  fluid  of  the  body.  It  is  the  source  of 
nourishment  for  all  the  cells.  Out  of  its  ingredients  the  tissues 
are  built.  It  contains  about  8.1  per  cent  of  water,  so  that  it 
easily  holds  in  solution  whatever  soluble  nutrients  are  furnished 
it  from  the  digestive  tract. 

The  19  per  cent  of  solids  consists  of  the  following  materials: 
10  per  cent  of  haemoglobin ;  7  per  cent  of  proteins ;  about  1  per 
cent  of  ash;  the  remaining  1  per  cent  consists  of  fats,  sugars, 
lecithin,  etc.  The  color  of  the  blood  is  due  to  haemoglobin.  This 
body  is  extremely  complex  in  composition  and  contains  about 
0.4  per  cent  of  iron.  Haemoglobin  is  a  dark  purplish-red  colored 
substance.  It  readily  combines  with  oxygen  to  an  oxy-compound 
which  is  bright  red  in  color.  The  haemoglobin  plays  an  import- 
ant part  in  respiration  as  the  carrier  of  oxygen  to  the  tissues. 

The  red  corpuscles  consist  of  circular,  bi-concave  discs,  though 
their  shape  and  size  vary  in  different  animals.  They  are  largest 
in  reptiles.  In  man  the  average  diameter  of  a  blood  corpusle  is 
about  1/3200  of  an  inch,  and  its  thickness  about  1/12800  of  an 
inch.  These  corpuscles  contain  the  haemoglobin,  the  coloring 
matter  of  the  blood.  When  they  are  treated  with  water  or  ether 
they  loose  their  coloring  matter  and  leave  a  nitrogenous  residue 
which  retains  the  shape  of  the  original  corpuscles. 

Bones  consist  of  an  earthy  frame  work  composed  mainly  of 
calcium  phosphate,  permeated  by  an  albuminoid,  called  ossein, 
and  by  nerves,  blood  vessels,  etc.  In  the  hollow  center  of  many 
bones  is  the  marrow,  which  consists  of  fats  and  proteins.  The 
relative  proportion  of  mineral  and  organic  matter  in  bones  varies 
considerably.  The  amount  of  mineral  matter  in  the  green  boi 


bone 

I 


The  Animal  Body.  213 

varies  from  40  to  60  per  cent.  No  definite  percentage  can  be 
given,  as  the  amount,  up  to  a  certain  limit,  will  vary  with  the 
supply  of  lime  and  phosphoric  acid  in  the  food  and  also  with 
the  source  of  the  bone. 

The  ash  of  bone  is  not  entirely  phosphate  of  lime,  but  contains 
in  addition  carbonates,  fluorides,  chlorides  and  magnesia.  The 
following  analysis  of  bone  ash  is  given  by  Ingle : 

Calcium  phosphate 86 . 0  per  cent 

Magnesium  phosphate 1.0        " 

Calcium,  as  carbonate,  chloride  and  fluoride. ..  7.3        "     . 

Carbon  dioxide 6.2        " 

Chlorine 0.2 

Fluorine 0.3        " 

Muscular  tissue  consists  largely  of  proteins  and  water,  but 
contains  in  addition  small  quantities  of  fat,  glycogen  (animal 
starch),  and  certain  nitrogenous  extractives,  such  as  creatin, 
ereatinin,  xanthin  and  guanin.  Small  quantities  of  dextrose  are 
also  contained  in  muscle  tissue.  The  ash  of  muscle  consists 
Largely  of  potash  and  phosphoric  acid  compounds,  but  there  are 
also  present  small  amounts  of  sodium,  magnesium,  calcium,  chlo- 
rine and  iron.  Muscle  usually  contains  about  75  to  80  per  cent 
of  water,  and  20  to  25  per  cent  of  solids. 

"When  a  muscle  does  work,  the  glycogen  and  sugar  are  burned 
at  an  increased  rate  and  the  blood,  which  bathes  the  muscle,  re- 
ceives an  increased  proportion  of  carbon  dioxide.  Fats  are  also 
sources  of  mechanical  work  for  the  muscle.  When  fats  and 
carbohydrates  are  available  for  consumption,  the  nitrogenous 
waste  of  the  muscle  is  not  increased  by  exercise,  and  only  the 
normal  amount  of  waste  nitrogenous  products,  as  urea,  uric  acid, 
etc.,  appear  as  the  result  of  the  life  processes. 

Fatty  tissue  is  made  up  of  relatively  large,  oval,  or  spherical 
cells.  These  cells  consist  of  a  nitrogenous  membrane,  filled  with 
fat,  which  during  life  is  fluid.  The  fats,  which  resemble  in  con- 
stitution the  vegetable  oils  already  described,  are  chiefly  com- 
posed of  stearin,  palmitin  and  olein.  The  fat  cells  may  be 


214  Agricultural  Chemistry. 

found  deposited  between  the  fibers  or  cells  of  muscular  tissue, 
or  may  constitute  almost  the  entire  mass  of  adipose  tissue. 
When  the  latter  is  the  case,  the  fatty  tissues  will  consist  of  water, 
membrane  and  fat  in  about  the  following  proportions: — 

Ox  Sheep  Pig 

Water         (percent) 9.96  10.48  6.44 

Membrane         "         1.16  1-64  1.35 

Fat  "         88.88  87.88  92.21 

Fat  is  stored  in  the  body  as  a  reserve  material  from  which  the 
animal  can  draw  in  time  of  scarcity  of  food.  It  is  the  most  con- 
centrated form  in  which  energy  is  stored  in  the  animal. 

Connective  tissue,  of  which  tendons,  ligaments,  cartilage  and 
skin  are  mainly  composed,  consists  of  substances  which  yield 
gelatine  when  heated  with  water.  These  are  the  albuminoid  com- 
pounds and  constitute  the  framework  of  the  animal  tissues.  Thej 
are  to  the  animal  body  what  cellulose  is  to  the  vegetable  kingdom, 
They  are  only  slightly  attacked  by  acids  and  alkalies  and  an 
insoluble  in  water  and  salt  solutions.  Several  different  bodies 
have  been  recognized,  among  which  are  elastin,  collagen  and 
keratin.  The  first  is  the  principal  constituent  of  the  elastic  tis< 
sues  and  contains  but  traces  of  sulphur.  The  second,  collagen, 
constitutes  the  foundation  of  cartilage  and  may  be  extracted  from 
these  tissues  with  hot  water.  The  product  which  goes  into  solu- 
tion is  called  gelatine  and  solidifies  on  cooling.  It  contains  about 
0.6  per  cent  of  sulphur.  The  third  substance,  keratin,  is  the  main 
constituent  of  hair,  horn,  hoof,  feathers  and  wool,  and  contains 
4  to  5  per  cent  of  sulphur.  It  is  insoluble  in  water,  but  by  heat- 
ing with  water  under  pressure  to  150-200°  C.  it  may  be  rendered 
soluble  and  then  constitutes  glue. 

Processes  of  nutrition.  We  have  seen  that  the  food  of  plants 
is  of  the  simplest  character  and  from  such  simple  materials  as 
carbon  dioxide,  nitrates,  certain  other  inorganic  salts  and  water. 
a  plant  is  able  to  construct  a  great  variety  of  complex  compounds. 
It  accomplishes  these  surprising  transformations  by  a  consump- 
tion of  energy  (sunlight)  external  to  itself.  An  animal  has  no 


The  Animal  Body.  215 

such  power.  The  animal  tissues  are  built  up  from  the  complex 
substances  existing  ready-formed  in  the  food.  The  animal  de- 
rives no  aid  from  external  energy.  The  temperature  of  the 
animal  body  (about  100°  F.)  is  maintained  by  heat  generated 
within  the  body  and  by  the  combustion  of  the  material  consumed 
as  food.  The  energy  by  which  all  the  mechanical  work  of  the 
animal  is  performed,  comes  from  the  same  source.  The  source 
of  heat  and  force  in  the  animal  is  thus  purely  internal. 

It  is  apparent  from  what  has  been  said  that  the  food  of  animals 
has  duties  to  perform  which  are  not  demanded  of  the  food  of 
plants.  In  plants  the  food  chiefly  provides  material  for  build- 
ing up  the  vegetable  tissues.  In  the  animal,  besides  constructing 
tissue,  the  food  must  furnish  the  means  of  producing  heat  and 
performing  mechanical  work;  to  accomplish  this  result,  it  must 
be  burned  in  the  animal  body. 

Functions  of  food  constituents.  The  solid  ingredients  of 
vegetable  food  may  be  classed,  as  (1)  proteins;  (2)  fats;  (3)  car- 
bohydrates; (4)  salts.  Besides  these  general  classes  of  food 
constituents,  we  have  in  immature  vegetable  products,  as  hays, 
roots,  etc.,  a  fifth  class — the  ammo-acids  and  amides — which  also 
take  part  in  animal  nutrition.  They  are  the  simple  intermed- 
iary nitrogenous  substances,  formed  from  the  nitrates  absorbed 
by  the  plant,  and  eventually  take  part  in  the  construction  of 
the  complex  proteins  of  seeds  and  plant  tissue. 

The  proteins  occurring  in  seeds,  roots  and  other  forms  of 
vegetable  food,  have  a  general  similarity  in  composition  to  those 
found  in  milk,  blood,  and  flesh,  but  are  by  no  means  identical. 
From  the  proteins  of  the  food  are  formed  not  only  the  proteins 
of  the  soft  tissues  of  the  animal,  but  also  such  a  class  of  proteins 
as  the  albuminoids,  which  differ  so  materially  in  properties  from 
the  proteins  of  blood  and  muscle.  It  is  also  very  probable  that 
fat,  a  non-nitrogenous  body,  may  be  formed  from  protein.  This 
is  still  a  much  disputed  question  and  it  remains  for  future  in- 
vestigations to  definitely  decide  this  point. 

Proteins  can  also  serve  as  a  source  of  energy.     In  the  case  of 


216  Agricultural  Chemistry. 

a  dog  eating  exclusively  a  meat  diet,  probably  a  greater  part  of 
the  protein  eaten  is  not  stored  but  is  used  as  fuel.  We  see  from 
this  that  the  proteins  can  serve  most  of  the  requirements  of  the 
animal,  a  statement  which  cannot  be  made  of  any  other  food 
constituent.  They  are  the  true  tissue  builders. 
H  An  animal,  even  when  not  increasing  in  weight,  will  always 
require  a  certain  constant  supply  of  protein  in  its  food  to  replace 
the  waste  of  nitrogenous  tissue,  which  is  always  going  on  even 
during  rest.  The  cell  proteins  are  constantly  undergoing  de- 
composition and  reconstruction. 

-"When  the  nitrogenous  tissues  of  the  animal,  or  the  proteins 
consumed  as  food  are  decomposed  in  the  body,  the  nitrogen  they 
contain  is  largely  excreted  in  the  form  of  a  simple  nitrogenous 
substance,  urea.  This  is  eliminated  by  way  of  the  kidneys  in  the 
urine.  There  are  small  quantities  of  other  nitrogenous  products, 
such  as  uric  acid,  creatin,  creatinin,  and  in  the  case  of  herbivora, 
hippuric  acid,  voided  in  the  urine,  but  they  constitute  but  a 
small  proportion  of  the  total  nitrogen  eliminated.  The  urea  pro- 
duced is  rich  in  nitrogen,  containing  about  46.6  per  cent.  It 
represents  about  one-third  the  weight  of  the  protein  oxidized. 

The  amides  and  amino-acids  consumed  as  food  are  burned  in 
the  body  and  their  nitrogen  excreted  as  urea.  It  is  very  prob- 
able that  they  can,  in  part,  take  the  place  of  proteins  as  tissue 
builders.  In  addition,  by  their  combustion,  they  serve  as  sources 
of  heat  and  force. 

The  fats  are  free  from  nitrogen.  Those  contained  in  food  are 
similar  to  those  found  in  the  animal  body.  It  appears  possible 
for  a  vegetable  fat  to  become  deposited  in  the  animal  without 
essential  change.  Small  deposits  occur  in  every  organ  and  cell. 
The  fat  reserves  vary  much  in  size,  depending  on  nutritive  con- 
ditions, so  that  no  definite  statement  can  be  made  regarding  the 
fat  content  of  the  individual  organs.  The  fat  of  the  food  is 
either  burned  in  the  animal  system  to  furnish  heat  and  mechan- 
ical energy  or  is  stored  up  as  reserve  material.  With  their  larger 
content  of  carbon  and  smaller  proportion  of  oxygen,  fats  are  less 


The  Animal  Body.  217 

easily  oxidized  than  sugars  and  require  a  larger  intake  of  oxygen 
for  their  combustion;  but  when  oxidized  they  yield  more  heat 
per  pound  than  any  other  food  ingredient. 

The  carbohydrates  of  the  food  are  chiefly  starch,  sugars,  cel- 
luloses and  pentosans.  Various  other  non-nitrogenous  constit- 
uents of  food,  such  as  the  pectins,  lignin  and  vegetable  acids, 
are  generally  included  under  this  title,  though  they  are  not, 
strictly  speaking,  carbohydrates.  Carbohydrates  form  the  larg- 
est part  of  all  vegetable  food.  They  are  not  permanently  stored 
in  the  animal  body,  but  serve  when  burned  in  the  system,  for 
the  production  of  heat  and  mechanical  work.  If  a  fattening 
steer  were  consuming  16  pounds  of  digestible  organic  matter  and 
gaining  two  pounds  of  live  weight  daily,  the  body  increase  and 
urine  would  contain  not  over  2.5  pounds  of  dry  matter,  leaving 
not  less  than  13.5  pounds  to  be  oxidized,  of  which  12  pounds 
might  consist  of  carbohydrates  and  fat,  mostly  the  former. 

The  carbohydrates  are  also  capable,  when  consumed  in  excess 
of  immediate  requirements,  of  conversion  into  fat.  The  well- 
recognized  value  of  corn  meal  as  a  fattening  food,  a  feeding  stuff 
nearly  seven-tenths  of  which  consists  of  starch  and  similar  struc- 
tures, is  a  practical  illustration  of  this  truth. 

The  carbohydrates  and  fats  are  the  natural  fuel  food  stuffs  of 
the  body.  They  cannot  serve  for  the  renewal  or  upbuilding  of 
tissue,  but  by  oxidation  they  constitute  an  economical  fuel  for 
maintaining  body  temperature  and  for  power  to  run  the  bodily 
machinery.  Proteins  may  likewise  serve  as  fuel,  but  this  is  ap- 
parently confined  to  a  non-nitrogenous  part  of  their  molecule. 
When  fats  or  carbohydrates  are  available  the  proteins  of  the  tis- 
sue are  not  normally  consumed  for  production  of  heat  and  force. 
Only  when  the  former  are  lacking  will  the  animal  increase  its 
protein  metabolism  and  nitrogen  output  for  purposes  of  main- 
taining the  body  temperature.  A  moderate  quantity  of  protein 
supplied  to  a  growing  animal  will  thus  produce  a  much  larger 
increase  of  muscle  when  accompanied  by  a  liberal  supply  of  car- 
bohydrates or  fats.  In  this  case,  the  non-nitrogenous  constit- 


218  Agricultural  Chemistry. 

uents  of  the  food  supply  the  demands  for  heat  and  work  and 
the  protein  can  be  devoted  to  the  rebuilding  or  increase  of  tissue. 

If  an  adult  animal  receives  the  small  amount  of  protein  and 
salts  necessary  to  repair  the  daily  waste  of  tissue,  it  would  be 
expected  that  the  whole  of  the  remaining  wants  might  be  met  by 
supplying  carbohydrates  or  fats.  This  is  to  some  extent  true; 
but  a  ration  very  poor  in  protein  is  not  found  to  be  consistent 
with  real  bodily  vigor.  There  is  some  specific  action  of  proteins 
not  as  yet  understood.  They  appear  to  stimulate  cell  activity, 
a  property  not  possessed  by  fats  and  carbohydrates. 

The  ash  constituents  present  in  food  are  the  same  as  those 
found  in  the  animal  body.  The  animal  simply  selects  from  the 
digested  ash  constituents  those  of  which  it  is  in  need.  The  tissue, 
the  blood,  digestive  fluids,  and  the  bony  framework  contain  a 
variety  of  these  bodies,  which  are  as  essential  as  any  of  the  other 
substances  considered  for  the  building  and  maintenance  of  the 
animal  body.  Without  lime  and  phosphoric  acid  there  can  be 
no  bone  formation,  and  the  digestive  juices  would  cease  to  be 
active  if  deprived  of  chlorine.  A  cow  from  which  common  salt 
is  withheld  will,  in  time,  die.  Not  only  must  the  growing  calf 
have  ash  material  for  constructive  purposes,  but  the  mature  ox 
must  be  supplied  with  them  in  order  to  sustain  the  nutritive 
processes.  The  milch  cow,  which  stores  combinations  of  lime, 
phosphoric  acid,  potash  and  other  salts  in  the  milk,  must  have 
an  adequate  supply  of  these  materials.  Nothing  else  can  take 
their  place.  Lime  and  phosphoric  acid,  stored  in  abundance  in 
the  framework  of  the  animal,  may  at  times  of  deficient  supply 
in  the  food,  act  as  internal  sources;  but  ultimately  all  ash  ele- 
ments must  have  been  contained  in  the  food. 

Digestion.  "We  have  accepted  so  far  without  discussion  the 
self-evident  fact  that  the  food  is  the  immediate  source  of  the 
energy  and  substance  of  the  animal  body.  It  is  now  necessary  to 
consider  the  way  in  which  the  nutrition  of  the  animal  is  accom- 
plished. Digestion  is  the  important  process  by  which  the  food 
of  an  animal  is  rendered  capable  of  being  absorbed  into  the  sys- 


The  Animal  Body. 

tern  and  utilized  in  building  up  or  renewing  the  tissue  of  the 
body.  Hay  and  grain  cannot  directly  be  transferred  to  the 
blood,  but  must  first  be  brought  into  soluble  and  diffusible  con- 
dition before  they  can  pass  out  of  the  alimentary  tract  into  the 
blood  and  lymph.  This  is  accomplished  partly  by  mechanical 
means,  but  mainly  by  chemical  changes,  which  are  produced 
chiefly  by  the  action  of  bodies  called  enzymes. 

Enzymes  are  a  peculiar  class  of  substances  produced  by  living 
cells  which  constitute  the  various  secreting  glands.  They  are  of 
unknown  composition  and  are  peculiar  in  that  the  chemical 
changes  which  they  induce  are  the  result  of  what  is  called  cat- 
alysis, or  contact.  That  is,  during  the  solution  of  the  food  stuffs, 
the  enzyme  is  not  used  up  or  destroyed,  but  by  its  mere  presence 
sets  in  motion  or  quickens  a  reaction  between  two  other  sub- 
stances. For  example,  the  enzyme  of  the  saliva  causes  the  starch 
of  the  food  to  combine  with  water,  with  the  result  that  the  soluble 
sugar  maltose,  is  formed.  An  enzyme  that  acts  upon  starch,  for 
example,  cannot  act  on  proteins  or  fats.  Some  digestive  fluids 
have  the  power  of  producing  changes  in  different  classes  of  food 
stuffs,  but  when  this  occurs,  it  is  assumed  to  be  due  to  the  presence 
in  the  same  fluid  of  different  enzymes.  Again,  enzymes  are  sen- 
sitive to  their  environment,  and  a  proper  temperature  and  re- 
action must  be  maintained  for  their  activity.  The  activity  of 
saliva  is  extremely  sensitive  to  the  nature  of  the  reaction  and 
ceases  when  that  becomes  acid.  Enzymes  are  thus  seen  to  be 
more  or  less  unstable  substances,  endowed  with  great  power  as 
digestive  agents,  but  sensitive  to  a  high  degree  and  working  ad- 
vantageously only  under  definite  conditions. 

Digestion  in  the  mouth.  The  first  step  is  mastication,  by 
which  the  food  is  subdivided  and  crushed  by  the  action  of  the 
teeth  and  thoroughly  mixed  with  saliva.  This  special  secretion 
has  its  origin  in  several  secreting  glands,  and  from  these  this 
liquid  is  poured  into  the  mouth  through  ducts,  opening  in  the 
cheek  under  the  tongue.  Saliva  is  a  highly  dilute  liquid  of  faint- 
ly alkaline  reaction  and  contains  an  enzyme,  ptyalin,  which  has 


220  Agricultural  Chemistry. 

the  power  of  bringing  about  the  same  changes  as  are  produced 
by  plant  diastase,  that  is,  the  conversion  of  starch  into  the  sugar, 
maltose.  This  change  begins  in  the  mouth  and  continues  for  a 
limited  time  in  the  stomach,  or  until  the  gastric  secretions  es- 
tablish an  acid  reaction  in  the  stomach  contents.  When  this  is 
established,  salivary  digestion  ceases.  The  proteins  and  fats  are 
not  attacked  by  the  salivary  secretion. 

Euminants,  whose  feed  usually  contains  much  starchy  material, 
secrete  enormous  quantities  of  saliva.  It  is  estimated  that  oxen 
and  horses  secrete  from  88  to  122  pounds  daily.  This  serves  the 
additional  important  function  of  properly  preparing  the  food 
for  swallowing. 

Gastric  digestion.  The  food  after  mastication  passes  down 
the  gullet  into  the  stomach.  In  the  case  of  the  horse  and  pig  the 
stomach  is  a  single  sac,  and  true  gastric  digestion  begins  at  once. 
In  ruminants,  as  the  ox  and  sheep,  the  stomach  consists  of  four 
divisions,  or  sacs,  and  not  until  the  fourth  is  reached,  does  gastric 
digestion  proper  begin.  These  sacs  may  be  considered  as  en- 
largements of  the  oesophagus  and  primarily  for  the  storage  of 
the  bulky  materials  consumed  by  these  classes  of  farm  animals. 
The  four  divisions  are  the  paunch,  honey-comb,  many-plies  and 
rennet,  or  what  the  anatomist  has  called  the  rumen,  reticulum, 
omasum  and  abomasum.  The  capacity  of  these  cavities  in  the 
ox  is,  on  the  average,  not  far  from  50  to  60  gallons,  about  nine- 
tenths  of  the  space  belonging  to  the  paunch.  It  is  in  the  paunch 
that  the  food  is  first  stored,  only  the  finer  portions  being  carried 
by  what  is  known  as  the  oesophagal  groove  to  the  third  stomach, 
and  finally  from  this  compartment  into  the  fourth  and  last  di- 
vision. From  the  paunch  the  food  is  returned  to  the  mouth 
where  it  is  more  finely  ground  before  passing  to  the  fourth  stom- 
ach for  digestion.  This  is  what  is  termed  ''chewing  the  cud." 
In  the  paunch  salivary  digestion  probably  continues,  as  well  as 
other  fermentations  induced  by  various  micro-organisms.  Here 
possibly  a  partial  fermentation  of  cellulose  by  bacterial  enzymes 
begins. 


The  Animal  Body. 


221 


When  the  food  reaches  the  fourth  stomach,  it  meets  with  the 
characteristic  secretion  of  that  organ,  the  gastric  juice.  This 
juice  is  secreted  by  glands  located  in  the  mucus  membrane  of 
the  stomach.  It  is  a  watery  fluid,  containing  various  salts,  as 
chlorides  and  phosphates  of  calcium,  magnesium,  sodium  and 
potassium,  free  hydrochloric  acid  and  the  two  enzymes,  pepsin 
and  rennin.  The  combination  of  pepsin  and  the  acid  is  the  ef- 


On  the  left — stomach  of  the  horse.  A,  end  of  the  oesophagus;  B,  pyloric 
end,  or  beginning  of  the  intestine.  On  the  right — stomach  of  the 
sheep.  O,  oesophagus;  P,  rumen;  R,  reticulum;  F,  omasum; 
C,  abomasum;  I,  commencement  of  the  small  intestine;  1,  oesophagal 
groove;  2,  opening  between  omasum  and  abomasum. 

fective  agent  in  the  digestion.  They  are  secreted  by  different 
gland  cells  in  the  stomach  walls  and  the  amount  of  hydrochloric 
acid  secreted  during  24  hours  by  a  normal  man,  under  ordinary 
conditions  of  diet,  amounts  to  what  would  constitute  a  fatal  dose 
of  acid,  if  taken  at  one  time  in  concentrated  form.  The  main 
action  of  gastric  juice  is  exerted  on  the  proteins  of  the  food, 
which  under  its  influence,  are  gradually  dissolved  and  converted 
into  soluble  products,  known  as  proteoses  and  peptones.  This 
enzyme,  like  the  ptyalin  of  the  saliva,  is  influenced  by  tern- 


222  Agricultural  Chemistry. 

perature,  maximum  digestive  action  being  manifested  at  about 
38°  C.,  the  temperature  of  the  body.  Further,  a  certain  degree 
of  acidity  is  essential  for  procuring  the  highest  degree  of  effi- 
ciency. Pepsin  acts  best  in  the  presence  of  from  0.1  to  0.3  per 
cent  of  free  hydrochloric  acid.  It  is  said  that  the  gastric  juice 
of  the  sheep  has  a  low  acidity,  while  that  of  the  dog  has  the  high- 
est recorded  among  mammals. 

Chemically,  the  results  are  the  same  in  the  stomachs  of  all  farm 
animals,  that  is,  the  proteins  are  changed  to  the  soluble  forms 
known  as  proteoses  and  peptones.  The  utilization  of  coarse  fod- 
der by  the  horse  is  not  as  complete  as  in  the  ox  for  the  reason 
that  in  the  case  of  the  former  there  is  no  preliminary  remastica- 
tion  and  trituration  before  the  food  material  comes  in  contact 
with  the  gastric  juice. 

Another  important  function  of  gastric  juice  is  that  of  curdling 
milk,  due  to  the  presence  in  the  secretion  of  the  peculiar  enzyme 
known  as  rennin.  This  is  present  in  the  stomach  of  all  mammal? 
and  it  is  the  calf's  active  secretion,  which  is  the  source  of  com- 
mercial rennet  used  in  cheese  making.  The  purpose  of  this 
enzyme  can  only  be  conjectured.  As  the  sole  nutriment  of  the 
young,  milk  occupies  a  peculiar  position  as  a  food  stuff,  and  be- 
ing a  liquid,  its  protein  constituents  might  easily  escape  complete 
digestion  were  it  to  pass  too  hastily  through  the  digestive  tract. 
Experiments  have  shown  this  to  be  true  of  liquid  foods.  But 
when  curdled  by  the  rennin,  the  proteins  of  the  milk  in  their 
clotted  state,  must  remain  for  a  longer  time  in  the  stomach,  and 
their  partial  digestion  by  gastric  juice  made  certain. 

Among  other  factors  in  gastric  digestion,  the  muscular  move- 
ments of  the  stomach  walls  are  to  be  emphasized,  since  we  have 
here  a  mechanical  aid  to  digestion  of  no  small  moment  and  like- 
wise a  means  of  accomplishing  the  onward  movement  of  the 
stomach- con  tents.  From  the  stomach  but  little  absorption  of  the 
soluble  food  materials  takes  place.  It  is  in  the  intestine  that  both 
digestion  and  absorption  are  at  their  best. 


The  Animal  Body.  223 

Digestion  in  the  intestine.  When  the  food  leaves  the  stomach 
it  enters  the  small  intestine.  At  this  point  it  is  only  partially 
digested.  The  fats  of  the  food  have  not  as  yet  been  changed, 
and  undoubtedly  a  considerable  proportion  of  the  proteins  and 
carbohydrates  susceptible  to  solution  is  still  to  be  acted  upon. 
Immediately  after  passing  from  the  stomach,  the  partially  di- 
gested mass  comes  in  contact  with  the  pancreatic  juice,  the  bile 
and  intestinal  juice,  and  the  changes  which  began  in  the  mouth 
and  stomach,  together  with  others  which  set  in  for  the  first  time, 
proceed  at  a  vigorous  rate.  The  bile  is  secreted  by  the  liver  and 
stored  in  the  small  sac  attached  to  that  organ  and  called  the 
"gall  bladder"  and  from  which  it  is  brought  to  the  intestine  by 
a  duct  opening  near  the  orifice  leading  out  of  the  stomach.  Bile 
is  a  reddish-yellow  (in  carnivorous  animals)  or  green  (in  herb- 
ivora)  liquid,  with  an  alkaline  reaction  and  bitter  taste.  It  con- 
tains complex  salts,  which  in  conjunction  with  the  fat  splitting 
enzyme  of  the  pancreatic  juice,  reduces  the  fats  to  an  emulsion, 
a  form  in  which  they  can  be  absorbed  into  the  blood.  When  bile 
is  prevented  from  entry  into  the  intestine,  the  fat  of  the  fowl 
largely  passes  out  in  the  feces.  Besides  this  important  relation 
to  fat  digestion,  the  bile  also  acts  in  some  degree  as  an  anti- 
septic, preventing  putrefaction  in  this  part  of  the  intestine. 

The  pancreatic  juice  is  of  strongly  alkaline  reaction  due  to  its 
content  of  sodium  carbonate,  and  is  characterized  by  the  pres- 
ence of  at  least  three  distinct  enzymes ;  these  are  trypsin,  a  pro- 
tein digesting  ferment ;  lipase,  a  fat  splitting  enzyme ;  and  amy- 
lopsin,  a  starch  digesting  enzyme.  This  juice  comes  from  the 
pancreas  and  enters  the  intestine  through  a  small  duct,  which 
in  some  animals  is  confluent  with  the  bile  duct.  By  the  action  of 
this  juice,  the  acid  chyme  from  the  stomach  is  rapidly  converted 
into  an  alkaline  mass  and  the  enzyme  pepsin  is  quickly  destroyed 
in  the  new  environment.  Trypsin,  effective  in  alkaline  media, 
now  continues  the  protein  digestion,  splitting  the  proteoses  and 
peptones,  as  well  as  unattacked  proteins,  into  simpler  structures. 
In  this  act  it  is  aided  by  another  enzyme,  known  as  erepsin, 


224  Agricultural  Chemistry. 

secreted  by  the  mucus  membrane  of  the  intestine.  These  two 
enzymes  are  powerful  agents  and  under  their  combined  action 
the  proteins  are  reduced,  in  part  at  least,  to  simple  fragments, 
the  amino-acids. 

The  fatty  foods  undergo  little  or  no  alteration  until  they  reach 
the  intestine.  While  in  the  stomach  they  become  liquid  from 
the  heat  of  the  body  and  the  neutral  fat  is  liberated  from  the 
cell  structures  by  the  action  of  the  gastric  juice.  Most  of  the 
neutral  fats  must  be  decomposed  into  the  fatty  acids  and  gly- 
cerine, of  which  they  are  composed,  before  absorption  into  the 
blood  can  take  place.  Under  the  influence  of  the  fat  splitting 
enzyme  of  the  pancreative  juice,  lipase,  and  the  bile  salts,  the 
neutral  fats  are  partly  decomposed,  with  formation  of  soaps. 
These  soaps  aid  in  the  formation  of  an  emulsion  of  the  rest  of 
the  fats.  Such  an  emulsion  is  really  a  suspension  of  the  fat  in 
a  very  finely  divided  condition.  Soap,  free  acid  and  glycerine 
are  then  absorbed  from  the  intestine  and  are  found  again  com- 
bined in  the  lymph  as  neutral  fat.  In  this  way  the  fats  are  ren- 
dered available  for  the  nourishment  of  the  body. 

The  transformation  of  starch  into  maltose  is  again  taken  up 
by  the  amylopsin  of  the  pancreatic  juice.  The  maltose  is  further 
exposed  to  an  enzyme  of  the  intestinal  juice,  termed  maltose, 
and  decomposed  into  the  simple  sugar,  dextrose.  Other  carbo- 
hydrates, as  the  lactose  of  milk,  and  cane  sugar,  meet  with  special 
enzymes  in  the  intestinal  juice,  capable  of  converting  them  into 
simple  sugars,  the  final  form  in  which  the  carbohydrates  are 
absorbed. 

No  special  enzymes  fermenting  the  celluloses  and  pentosans, 
which  constitute  a  large  proportion  of  hays  and  straws,  have  as 
yet  been  prepared  from  the  normal  secretions  of  the  intestinal 
tract.  Possibly  their  partial  solution  is  effected  by  bacterial  fer- 
ments and  other  low  forms  of  life.  Such  solution  may  have  its 
beginning  in  the  paunch,  where  active  fermentations  are  in 
progress,  and  continue  in  the  lower  portions  of  the  digestive  tract. 


The  Animal  Body.  225 

Absorption  of  food.  In  the  ways  mentioned  above,  the  pro- 
teins, fats  and  carbohydrates  of  the  food  are  gradually  digested. 
Throughout  the  length  of  the  small  intestine  absorption  proceeds 
rapidly;  water,  salts  and  the  products  of  digestion  pass  out 
from  the  intestine  into  the  circulating  lymph  and  blood.  There 
are  two  pathways  by  which  absorbed  material  reaches  the  blood. 
In  the  intestinal  wall  are  numerous  projections,  called  villi.  Im- 
bedded in  these  structures  are  the  minute  branches  of  two  sys- 
tems of  vessels.  One  set  is  the  lacteals,  belonging  to  the  lym- 
phatic system  and  the  other  the  capillaries  of  the  blood  system. 
Materials  passing  into  the  lacteals  reach  the  thoracic  duct  and  by 
it,  in  a  roundabout  way,  are  carried  into  one  of  the  main  blood- 
vessels at  the  neck.  As  a  general  truth  it  may  be  stated  that  the 
fats  are  largely  absorbed  through  this  channel,  and  it  is  impor- 
tant to  observe  that  when  they  reach  the  lacteals  they  are  again 
in  the  form  of  neutral  fats. 

Materials  absorbed  by  the  capillaries  of  the  blood  system  are 
carried  directly  to  the  liver  through  the  portal  vein,  and  there 
subjected  to  the  action  of  that  organ  before  they  enter  the  gen- 
eral circulation.  Most  salts  and  the  carbohydrates  and  proteins 
follow  this  course.  In  the  liver  the  soluble  sugars  are  converted 
into  glycogen,  the  animal  starch,  and  as  such  temporarily  stored. 
The  amount  of  sugar  in  the  blood  is  a  constant  but  small  quan- 
tity and  as  this  is  required  in  the  tissue,  the  glycogen  is  recon- 
verted back  into  soluble  sugar  to  maintain  the  supply  in  the 
blood. 

The  fragments  of  protein  digestion,  the  proteoses,  peptones 
and  amino-acids,  are  not  found  as  such  in  the  blood  or  at  least 
only  in  traces.  Either  in  passing  through  the  intestinal  wall, 
or  after  reaching  the  liver,  they  are  reconstructed  into  complex 
proteins  before  being  cast  loose  into  the  circulatory  system. 
These  reconstructed  proteins  are  the  serum  albumin,  serum  glo- 
bulin and  haemoglobin  of  the  blood,  which  serve  as  sources  of 
protein  for  the  various  body  tissues.  The  processes  of  absorption 


226  Agricultural  Chemistry. 

and  blood  regulation  are  wonderfully  and  delicately  balanced  and 
are  by  no  means  completely  understood. 

Feces.  The  portion  of  the  food  which  has  escaped  solution 
and  absorption,  together  with  certain  substances  already  absorbed 
but  re-excreted  by  way  of  the  intestines,  constitute  the  feces. 
Epithelial  cells  from  the  intestinal  walls,  parts  of  the  digestive 
juices,  bile,  bacterial  cells,  etc.,  will  make  up  a  large  portion  of 
the  fecal  matter. 

Respiration.  The  nutrients,  prepared  by  the  various  process- 
es of  solution  and  reconstruction  in  the  intestines  and  intestinal 
wall,  enter  the  blood  on  its  return  to  the  heart,  coming  into  the 
venous  circulation  by  way  of  the  thoracic  duct  and  liver  (hep- 
atic vein),  as  already  described.  By  this  route,  the  blood,  laden 
with  nutrients,  passes  to  the  right  side  of  the  heart.  It  is  then 
carried  to  the  lungs,  by  way  of  the  right  ventricle,  to  be  returned 
to  the  left  side  of  the  heart,  and  from  which  it  is  pumped  to  all 
parts  of  the  body.  In  the  lungs  the  blood  is  supplied  with  oxy- 
gen. The  purple  of  venous  blood  is  changed  to  a  scarlet,  due 
to  the  absorption  of  oxygen  by  the  haemoglobin,  with  the  forma- 
tion of  oxy-haemoglobin,  the  important  oxygen  carrier  of  the 
blood.  At  the  same  time,  a  considerable  quantity  of  carbon 
dioxide,  most  of  which  was  in  solution  in  the  blood  plasma,  pos- 
sibly as  a  bi-carbonate,  is  given  up  to  the  air  within  the  lungs. 

Inspired  air  contains  about  21.0  per  cent  of  oxygen  and  .03 
per  cent  of  carbon-dioxide,  while  expired  air  carries  approx- 
imately 16.5  per  cent  of  oxygen  and  4.4  per  cent  of  carbon-diox- 
ide<  Though  the  absorption  of  oxygen  takes  place  in  the  lungs, 
it  is  not  there  that  the  processes  of  combining  the  oxygen  with 
the  carbon  and  hydrogen  of  the  body  tissues  takes  place.  The 
blood,  through  the  haemoglobin  of  the  red-blood  corpuscles,  acts 
as  a  carrier  of  oxygen  and  the  actual  combustion  of  the  products 
derived  from  the  food  occurs  in  the  tissues  themselves.  The  rate 
of  combustion  in  the  tissues  is  a  variable  one,  dependent  upon 
the  amount  of  work  the  animal  is  doing  and  the  temperature  to 


The  Animal  Body.  227 

which  it  is  exposed.  And  it  is  through  this  oxidation  of  the 
nutrients  in  the  cells  of  the  body  that  heat  and  mechanical  work 
are  produced. 

Elimination.  As  has  already  been  noted,  the  undigested  resi- 
dues of  food,  together  with  certain  excretory  products  eliminated 
by  way  of  the  intestines,  constitute  the  feces. 

The  products,  which  result  from  the  metabolism  of  the  body 
cells,  or  of  the  food  consumed,  are  removed  from  the  body  by  the 
lungs,  the  kidneys,  the  skin  and  the  intestine.  The  carbohyd- 
rates and  fats,  which  are  oxidized  in  keeping  up  the  animal  heat 
or  in  furnishing  energy,  are  broken  down  into  carbon-dioxide 
and  water  and  removed  as  such  from  the  blood  in  the  lungs,  and 
to  a  smaller  extent  by  the  skin.  Water  and  salts  are  removed  by 
both  intestine  and  kidney,  while  the  perspiration  may  also  serve 
to  carry  considerable  quantities  of  these  materials.  The  elimina- 
tion of  the  products  of  protein  degradation  in  the  tissues  is  al- 
most entirely  by  way  of  the  kidneys.  The  larger  part  of  the 
nitrogen  is  eliminated  in  the  form  of  the  simple  body,  urea.  There 
are  other  forms  of  nitrogen  occurring  in  the  urine,  such  as  uric 
acid,  creatin,  creatinin,  ammonia,  etc.,  but  they  constitute  only  a 
small  proportion  of  the  total  nitrogen  eliminated. 

The  sulphur  of  the  protein  molecule  is  also  removed  as  sulphate 
through  the  kidney,  while  the  phosphorus  passes  out  of  the  body 
in  the  form  of  a  phosphate  by  both  the  intestines  and  kidney; 
by  far  the  larger  proportion  is  removed  through  the  intestine  in 
the  herbivora. 

The  quantity  of  nitrogen  in  the  urine  is  taken  as  a  measure  of 
the  amount  of  protein  decomposition  in  the  tissue.  This  may  be 
only  partly  true.  It  is  now  believed  that  a  considerable  part  of 
the  nitrogen  of  ingested  protein  has  not  been  built  into  body 
tissue,  but  is  eliminated  from  the  protein  molecule  as  ammonia 
in  the  intestine,  carried  to  the  liver,  and  from  there  finally  ex- 
creted through  the  kidney  as  urea.  The  carbonaceous  part  of 
the  protein  molecule  from  which  this  nitrogen  has  been  removed 


228 


Agricultural  Chemistry. 


may  now  be  used,  through  combustion,  as  a  source  of  energy  for 
the  animal  body. 

When  an  animal  is  supplied  with  known  quantities  of  food  per 
day,  it  is  possible,  by  collecting  the  feces  and  subjecting  it  to  the 
same  chemical  analysis  as  was  applied  to  the  food,  to  determine 
how  much  of  each  constituent  of  the  food  has  been  digested  by 
the  animal.  This  applies  particularly  to  carbohydrates,  fats  and 
proteins,  although  not  strictly  accurate  for  these.  It  does  not 
apply  to  the  mineral  salts,  as  they  are  partly  excreted  through 
the  intestine.  But  by  such  means  the  digestibility  of  feeds  is 
measured  and  such  results  are  of  enormous  value  to  the  knowledge 
of  animal  feeding. 


CHAPTER  X 
FEEDING  STANDARDS 

We  have  traced  in  the  preceding  chapter  the  processes  of  solu- 
tion and  the  destination  of  the  various  nutrients  of  feeding  ma- 
terials. It  will  now  be  necessary  to  consider  briefly  the  develop- 
ment of  our  knowledge  leading  to  the  establishment  of  feeding 
standards  and  the  present  status  of  such  information.  In  1810 
Thaer,  in  Germany,  formulated  the  first  standard,  publishing  a 
table  of  hay  equivalents,  using  meadow  hay  as  the  standard.  It 
had  little  experimental  foundation  and  soon  fell  into  disuse.  In 
1859  Grouven  published  the  first  standard  based  upon  the  quan- 
tity of  proximate  constituents  in  feeding  materials. 

The  work  of  Liebig,  Boussingault,  and  others,  with  the  new 
tools  of  a  rapidly  developing  chemistry,  was  paving  the  way  for 
standards  based  on  chemical  analysis.  But  the  tables  of  Grouven 
did  not  meet  the  requirements,  since  they  were  -based  on  the  total, 
instead  of  the  digestible  nutrients. 

In  1864  the  feeding  standards  of  Wolff,  the  eminent  German 
scientist,  first  appeared.  They  are  based  upon  the  amounts  of 
digestible  protein,  carbohydrates  and  fats,  required  by  the  va- 
rious classes  of  farm  animals.  These  standards  have  been  pub- 
lished annually  in  the  Mentzel-Lengerke  calendar  down  to  1896 ; 
for  the  next  ten  years  they  were  issued  by  Lehmann  of  the  Berlin 
Agricultural  High  School,  and  since  1907  by  Kellner,  modified 
to  a  starch  equivalent  basis,  to  be  described  later.  The  Wolff 
standards  have  seen  wide  use  by  practical  stockmen  because  of 
their  simplicity  and  definiteness. 

Co-efficient  of  digestibility.  The  nutrients  of  feeds  are  not 
wholly  digestible.  A  part  passes  through  the  animal  without 
having  been  dissolved  by  the  digestive  juices  and  thereby  made 
available  to  the  animal.  The  general  method  of  measuring  the 
digestibility  of  feeds  has  been  to  supply  the  animal  with 


230 


Agricultural  Chemistry. 


quantities  of  the  feed,  the  composition  of  which  has  been  de- 
termined by  chemical  analysis.  During  the  experiment  the  solid 
excrement  is  collected  and  weighed  and  finally  analyzed  by  the 
same  methods  as  those  previously  applied  to  the  feed.  From  the 
data  thus  collected  the  digestion  co-efficients  are  calculated. 
Example : 

Digestion  Experiment  with  Sheep  (From  Henry). 


Nitro- 

Dry 
Matter 

Protein 

Crude 
fiber 

gen 
free 

Ether 
extiact 

extract 

Grams 

Grams 

Grams 

Gra  ms 

Grams 

Fed  700  grams  of  hay    (con- 

586.1 

77  7 

191.7 

276.7 

10.7 

Excreted    610.6   grams    dung 

288.6 

40  4 

101.5 

119  4 

7.9    , 

Digested  

297.5 

37.3 

90.0 

157.3 

2  8 

Per  cent  digested  . 

50  8 

48  0 

47  1 

56  8 

26  2 

From  the  example  it  will  be  seen  that  the  digestion  co-efficient 
is  the  proportion  of  each  food  constituent  digested  out  of  100 
parts  by  weight  supplied.  The  figures  secured  are  not  absolutely 
accurate,  due  to  intestinal  secretions  which  become  reckoned  as 
undigested  food.  The  co-efficients  for  proteins  and  fats  suffer 
most  in  this  regard.  In  experiments  with  oat  straw  the  fecal  nit- 
rogen has  been  found  to  be  more  than  that  in  the  food,  although 
the  protein  of  the  straw  must  have  been  digested  to  a  considerable 
extent.  Jordan  states:  "It  is  probably  safe  to  affirm  that  at 
least  10  should  be  added  to  the  co-efficients  of  digestibility  of  the 
protein  of  coarse  fodders,  as  usually  given  in  the  tables  that  have 
been  compiled."  With  fat  co-efficients,  an  error  is  introduced 
through  the  secretion  of  bile  into  the  intestine.  This  material 
contains  products  soluble  in  ether,  the  usual  reagent  used  in  de- 
termining the  fat  content  of  the  feeding  stuff.  Consequently  the 
undigested  fat  appears  larger  than  it  really  is. 


Feeding  Standards.  231 

Conditions  affecting  digestibility.  Animals  differ  in  their 
power  of  digesting  any  given  food  or  food  constituent.  For  ex- 
ample, the  ruminants,  by  their  more  thorough  arul  repeated  mas- 
tication, are  better  able  to  digest  bulky  fodder  than  are  pigs  and 
horses.  This  is  illustrated  in  the  following  table  taken  from 
Jordan : — 

Dry  Substance  Digested  from  Meadow  Hay  (Per  Cent). 

Samples  Best  Medium  Poor 

Sheep 42  67  61.  55    - 

Oxen 10  67  64  56 

Horses 18  58  50  46 

On  the  other  hand  the  power  of  digesting  bulky  feeds  by  dif- 
ferent classes  of  ruminants  is  very  similar.  Steers  have  been 
compared  with  sheep,  and  cows  with  goats,  with  no  uniform  dif- 
ference in  their  digestive  power  for  this  class  of  feeds. 

With  the  grains,  the  differences  in  digestibility  with  the  various 
classes  of  farm  animals  are  not  greatly  unlike.  Comparative 
trials  of  oats  with  sheep  and  the  horse  gave  nearly  identical  di- 
gestibility of  the  dry  matter.  With  cows  the  result  was  similar. 
In  other  trials  where  beans  were  used  the  advantage  was  slightly 
with  the  ruminant.  Swine  digest  the  concentrated  feeds  as  com- 
pletely as  do  ruminants  or  the  horse.  Nor  are  they  incapable  of 
digesting  vegetable  fiber  when  presented  in  a  favorable  condi- 
tion. Pigs  fed  on  green  oats  and  vetch  digested  48.9  per  cent 
of  the  fiber  supplied.  However,  the  digestive  apparatus  of  the 
pig  is  not  adapted  for  dealing  successfully  with  bulky  fodder. 

So  far  as  the  influence  of  breed  is  concerned,  this  does  not  be- 
come a  factor  in  the  digestibility  of  feeds.  A  Jersey  is  as  effi- 
cient in  this  capacity  as  a  Holstein.  Young  animals  appear  to 
digest  as  efficiently  as  older  ones  of  the  same  species.  There  are, 
very  probably,  differences  in  individuals,  but  the  data  so  far 
collected  do  not  definitely  show  this. 

The  influence  of  quantity  of  food  on  digestion  is  an  unsettled 
point.  The  old  experiments  of  Wolff  indicated  that  a  full  ration 
was  as  completely  digested  as  a  scanty  one.  More  recent  ex- 


232  Agricultural  Chemistry. 

periments  in  Europe,  as  well  as  in  this  country,  give  opposite 
results,  indicating  a  higher  rate  of  digestibility  with  smaller 
rations.  The  difference  is  not  large  and  with  appetite  regulating 
the  consumption,  it  is  fair  to  assume  that  variations  in  food  in- 
take, incidental  to  normal  feeding,  will  not  markedly  influence 
the  power  of  digestion. 

influence  of  the  quality  of  feed  on  digestibility.  It  is  a  popu- 
lar belief  that  curing  a  fodder  decreases  its  digestibility.  This  is 
probably  true,  especially  where  the  drying  has  been  conducted 
in  a  careless  manner.  The  loss  of  leaves  and  the  finer  parts  of 
the  plant,  and  the  washing  out  of  soluble  matter  by  rain  are 
factors  which  will  depress  the  digestibility  of  the  fodder.  For 
this  reason,  field  cured  corn  fodder  is  considerably  less  digestible 
than  silage  coming  from  the  same  source.  On  the  other  hand, 
where  the  curing  is  done  in  such  a  manner  as  to  exclude  these 
losses,  it  is  doubtful  if  it,  in  itself,  has  any  appreciable  effect 
upon  digestibility. 

The  stage  of  growth  of  a  fodder  plant  will  influence  its  di- 
gestibility. That  stage  where  there  is  a  relatively  high  propor- 
tion of  starch  and  sugar  and  a  minimum  of  cellulose  and  lignins, 
will  show  a  higher  digestibility.  As  the  grasses  mature,  the  fiber 
increases;  on  the  other  hand,  the  corn  plant  furnishes  a  rela- 
tively higher  proportion  of  digestible  nutrients  when  the  ears 
are  full  grown  than  before  the  ears  have  formed. 

Influence  of  methods  of  preparation.  Steaming,  wetting  and 
cooking  the  feed  have  received  considerable  attention.  The  gen- 
eral concensus  of  opinion  of  feeders,  as  well  as  the  results  of 
scientific  experiments,  do  not  indicate  that  these  practices  are 
of  great  advantage ;  beans,  corn  and  bran  are  not  better  digested 
by  the  horse  or  ox  when  previously  soaked  in  water.  Barley, 
corn  and  pea  meal  have  been  found  more  nourishing  for  pigs 
when  given  dry  than  when  previously  cooked.  Cooking  certainly 
depresses  the  digestibility  of  the  proteins.  This  has  been  ex- 
perimentally demonstrated  with  steamed  hays,  silage,  corn 


Feeding  Standards.  233 

and  wheat  bran.  However,  when  cooking  or  steaming  the  feed 
renders  it  more  palatable,  and  secures  a  larger  consumption  of 
material  which  otherwise  would  be  wasted,  the  influence  on  di- 
gestibility is  of  less  importance. 

Grinding  increases  the  digestibility  of  feeds.  Mechanical  divi- 
sion is  an  important  factor  in  the  rate  and  completeness  of  solu- 
tion of  material  in  the  digestive  tract.  A  single  experiment  with 
corn,  fed  to  the  horse,  showed  about  7  per  cent  increased  digesti- 
bility from  grinding,  and  with  wheat,  in  one  trial  the  increase 
was  10  per  cent.  With  ruminants,  the  danger  from  imperfect 
mastication  is  less  than  with  horses  and  swine.  Whether  it  will 
pay  to  grind  the  grain  will  depend  upon  the  cost  of  grinding 
and  the  loss  of  nutritive  material  from  not  grinding. 

Influence  of  one. feed  on  the  digestibility  of  another.  It  is 
generally  stated  that  the  addition  of  a  considerable  quantity  of 
protein  to  a  ration  of  hay  and  straw  consumed  by  a  ruminant, 
is  completely  digested,  without  affecting  the  digestibility  of  the 
original  feed.  Pigs  have  been  fed  potatoes  to  which  variable 
quantities  of  meat  flour  were  added.  The  proteins  of  the  meat 
were  completely  digested,  while  the  proportion  of  potatoes  di- 
gested remained  unchanged. 

It  is  also  claimed  that  the  addition  of  fat  or  oil  to  a  basal 
ration  of  hay  and  straw  was  without  influence  on  their  digesti- 
bility. 

On  the  contrary,  Dietrich  and  Koenig  state  that  if  a  carbo- 
hydrate, as  starch  or  sugar,  is  added  to  the  extent  of  more  than 
10  per  cent  of  the  dry  substance  of  a  basal  ration,  or  if  roots  or 
potatoes,  equivalent  in  dry  matter  to  more  than  15  per  cent,  are 
fed,  a  diminution  of  digestibility  occurs.  It  is  further  stated 
that  the  depression  of  digestibility  is  reduced,  when,  accompany- 
ing the  high  starch  intake,  there  is  a  corresponding  increase  in 
protein  consumption.  Prom  these  considerations,  it  is  stated 
that  highly  nitrogenous  feeds  may  be  given  with  hay  and  straw 
without  affecting  their  digestibility;  but  feeds  rich  in  carbohyd- 


234  Agricultural  Chemistry. 

rates,  as  potatoes  and  mangels,  cannot  be  given  in  greater  pro- 
portion than  15  per  cent  of  the  fodder  (both  calculated  as  dry 
food)  without  diminishing  the  digestibility  of  the  latter. 

Lindsey  of  the  Massachusetts  Station  has,  in  part,  confirmed 
the  work  of  Dietrich  and  Koenig.  He  found  that  when  Porto 
Rico  molasses  fed  together  with  hay,  constituted  from  10  to  15 
per  cent  of  the  total  dry  matter  of  the  ration,  little  if  any  de- 
pression occurred.  But  with  molasses  constituting  20  per  cent 
of  the  dry  matter  of  the  ration,  a  depression  of  4.5  per  cent  was 
noted  in  the  digestibility  of  the  hay.  He  concluded  that  molasses 
and  hay  would  not  make  a  satisfactory  combination  for  farm 
stock.  A  more  suitable  ration  would  consist  of  hay,  together 
with  one  or  more  protein  concentrates  and  molasses.  Even  in  a 
ration  of  hay  and  gluten  feed  and  in  which  molasses  composed 
20  per  cent  of  the  dry  matter,  there  was  a  depression  of  8  per 
cent  in  the  digestibility  of  the  hay  and  gluten. 

The  nutritive  ratio.  We  have  seen  that  the  formulation  of 
feeding  standards  must  be  based  on  a  knowledge  of  the  relative 
digestibility  of  the  several  nutrients  contained  in  the  feeding 
material.  Such  knowledge  has  been  secured  by  many  experi- 
menters, working  with  various  classes  of  farm  animals,  and  has 
given  us  our  tables  of  co-efficients  of  digestibility  available  in 
books  on  animal  feeding.  (See  table  in  Appendix.) 

It  has  been  found  in  practice  that  the  feed  of  an  animal  may 
be  varied  within  fairly  wide  limits,  provided  the  ratio  of  digest- 
ible protein  to  all  other  digestible  organic  matter  is  kept  within 
certain  limits.  Protein  has  special  and  peculiar  functions  and 
less  than  a  certain  minimum  would  limit  production  by  just  the 
amount  of  the  deficiency.  In  order  to  get  this  ratio  it  is  neces- 
sary that  some  carbohydrate  be  taken  as  a  standard  for  express- 
ing the  non-protein  portion  of  the  ration.  Starch  is  the  sub- 
stance always  chosen,  and  it  becomes  necessary,  in  order  to  ex- 
press the  fats  and  other  carbohydrates  in  terms  of  starch,  to  ob- 
tain the  equivalent  in  heat  producing  power  of  the  other  food 
constituents.  This  has  been  secured  (1)  by  burning  a  weigher! 


Feeding  Standards.  235 

portion  of  the  various  materials  in  a  calorimeter  (an  instrument 
for  measuring  heat  production),  and  (2)  by  direct  experiments 
upon  animals  placed  in  a  respiration  calorimeter  (an  apparatus 
for  measuring  both  gas  and  heat  production) ,  and  fed  with  known 
weights  of  the  various  feeding-stuffs.  As  an  average  of  several 
experiments  it  may  be  taken  that  one  part  of  fat  evolves  as  much 
heat  as  2.4  parts  of  starch,  sugar,  cellulose  or  of  protein.  To 
express  the  non-protein,  other  than  carbohydrates,  in  terms  of 
starch,  it  is  therefore  necessary  to  multiply  the  quantity  of  di- 
gestible fat  by  2.4  and  add  this  product  to  the  quantity  of  digest- 
ible carbohydrates  present.  The  nutritive  ratio  thus  becomes : 

digestible  protein 


digestible  carb.  +  (dig.  fat  X  2.4) 
The  nutritive  ratio  of  corn  meal  is  obtained  as  follows: 

100  Ibs.  contain    7.9  Ibs.  digestible  protein 

66.7  Ibs.  digestible  carbohydrates 
4.3  Ibs.  digestible  ether  extract  (fat) 

7.9  7.9  7.9  1 


66.7  +  (4.3  X  2.4)  66.7  +  9.32          76.02          9.6 

The  nutritive  ratio  for  corn  meal  is  therefore  1 :9.6.  This 
means  that  for  every  pound  of  digestible  protein  in  corn  meal 
there  are  9.6  pounds  of  digestible  carbohydrates  and  ether  ex- 
tract (fat)  equivalent.  The  term  "wide"  ratio  is  used  when 
there  is  a  very  large  proportion  of  carbohydrates  contained  in  a 
feed  in  proportion  to  the  protein.  Oat  straw,  with  a  nutritive 
ratio  of  1:33.7,  is  an  example  of  a  very  "wide"  nutritive  ratio. 
With  corn  the  ratio  is  "medium,"  while  with  oil  meal,  with  a 
ratio  of  1:1.7  the  expression  "narrow"  is  used. 

The  Wolff-Lehman  feeding  standards.  In  1864  Wolff  pro- 
posed certain  feeding  standards,  which  have  been  largely  used  in 
framing  rations.  In  order  to  eliminate  the  size  of  the  animal, 
'the  proportion  of  the  various  feed  constituents,  to  be  supplied 
daily  for  1000  pounds  of  body  weight,  are  given.  For  illustra- 
tion, a  few  standards  are  given  here.  (See  full  table  in  Ap- 
pendix.) 


236 


Agricultural  Chemistry. 
For  1000  Pounds  Live  Weight  Daily. 


Dry 

Digestible 

Nu- 

Sub- 
stance 

Protein 

Carbo- 
hydrates 

Fat 

tritive 
Ratio 

Cow  milk  yield  22  Ibs  

Lbs. 
29 

Lbs. 
2  5 

Lbs. 
13 

Lbs. 
0  5 

1  -5  7 

Fattening  steer,  1st  period.. 
Horse,  medium  work  

30 
24 

2.5 

2.0 

15 
11 

0.5 
0.6 

1:6  5 
1:6.2 

In  formulating  standards  for  ruminants  it  is  better  to  start 
with  two  kinds  of  roughage,  furnishing  from  16  to  20  pounds  of 
dry  matter,  and  about  10  pounds  of  carbohydrates  (nitrogen 
free-extract) ,  and  then  add  concentrates,  which  will  on  first  cal- 
culation bring  the  total  digestible  protein  somewhat  under  the 
standard.  The  additional  requirements  can  then  be  easily  com- 
puted. The  term  "fat"  is  identical  with  the  "ether  extract." 

It  is  not  necessary  that  a  ration  agree  mathematically  in  all 
nutrients  with  the  standard.  To  attempt  to  do  this  is  to  avoid 
the  individual  possibilities  of  the  animal.  The  tables  of  digestion 
co-efficients  and  feeding  standards  are  but  averages  and  approx- 
imations. They  are  not  to  be  followed  blindly  and  absolutely, 
but  if  taken  as  guides,  they  can  become  extremely  helpful.  For 
example,  the  Wolff  standards  are  quantities  to  be  fed  per  thou- 
sand pounds  of  live  weight.  It  is  known  that  the  food  demands 
of  an  organism  are  not  proportional  to  its  size,  but  rather  to  its 
surface.  This  is  because  of  a  difference  in  demand  on  the  heat 
producing  function  of  a  food.  A  small  animal  has  a  propor- 
tionately greater  suface  to  its  weight  than  a  larger  animal.  Con- 
sequently it  does  not  require  the  same  proportional  amount  of 
digestible  food  to  maintain  a  1700  pound  steer  as  one  weighing 
]  000  pounds.  For  instance,  Kuhn  of  the  Mockern  Station,  found 
that  a  1900  pound  ox  could  be  maintained  on  0.7  pound  of  di- 
gestible protein  and  6.6  pounds  of  digestible  carbohydrates. 


Feeding  Standards.  237 

Other  investigators  have  found  that  the  Wolff  allowances  may  be 
too  high.  Haecker  of  the  Minnesota  Station  maintained  a  dry. 
barren  cow  of  a  1000  pounds  weight  on  0.6  pound  of  digestible 
protein,  6  pounds  of  digestible  carbohydrates,  and  0.1  pound  of 
digestible  fat  (ether  extract). 

Energy  value  of  feeds.  The  function  of  food,  as  has  already 
'  been  pointed  out,  is  not  only  to  repair  waste  and  promote  growth 
and  increase,  but  also  to  furnish  heat  and  energy.  For  this 
reason,  attempts  have  been  made  by  several  investigators  to  assess 
the  relative  value  of  feeds  by  a  determination  of  their  heat  pro- 
ducing power.  Heat  units  are  expressed  either  in  starch  equiv- 
alents or  calories.  The  German  investigators,  Kellner  and  Zuntz, 
have  used  starch  as  the  basis  for  expression,  while  Armsby  of 
this  country  is  using  the  calorie.  The  calorie  represents  the 
quantity  of  heat  required  to  raise  the  temperature  of  one  gram 
of  water  from  0°  to  1°  C.  A  large  Calorie,  one  thousand  times 
larger  than  the  small  calorie,  is  usually  employed  for  the  ex- 
pression of  large  quantities  of  heat  and  will  be  used  here,  gen- 
erally. However,  the  new  term,  therm,  which  represents  1000 
large  Calories,  is  now  in  use  by  Armsby  and  is  the  quantity  of 
heat  required  to  raise  the  temperature  of  1000  kilograms  of 
water  1°  C. 

The  value  in  large  Calories  of  one  gram  of  the  several  classes 
of  nutrients,  is  given  in  the  following  table : 


Wheat  gluten 5.8 

Animal   muscle 5.7 

Starch..  4.1 


Cellulose 4.1 

Cane  sugar ^ .  0 

Animalfat..  9.4 


Available  energy.  The  data  in  the  above  table  is  secured  by 
complete  combustion  of  the  material  in  the  calorimeter.  Such 
does  not  obtain  in  the  animal  body.  It  should  be  remembered 
that  only  part  is  digested,  and  as  only  the  digested  portion  fur- 
nishes available  energy,  the  available  fuel  value  of  a  ration  must 
depend  primarily  upon  the  amount  which  is  dissolved  out  of  the 
digestive  tract  and  passes  into  the  blood.  There  is  fuel  waste  in 
the  solid  excrement  of  the  feces,  in  the  incompletely  burned  gases 


238  Agricultural  Chemistry. 

escaping  from  the  alimentary  canal,  and  in  the  unoxidized  com- 
pounds of  the  urine.  It  has  been  estimated  by  Kuhn  that  the 
loss  of  energy  in  the  gas,  methane,  which  has  its  source  in  the 
fermentations  of  the  digestive  tract,  amounts  to  over  one-seventh 
of  the  energy  of  the  digested  crude  fiber  and  carbohydrates. 
From,  this  we  see  that  the  available  energy  of  a  ration  represents 
the  fuel  value  of  the  dry  matter  digested  from  it,  minus  the 
energy  in  the  dry  'matter  of  the  urine  and  that  lost  in  excreted 
gases.  Such  data  have  been  secured  on  a  number  of  materials 
by  the  use  of  the  respiration  apparatus — an  air  tight  compart- 
ment in  which  the  animal  could  live  and  from  which  the  gases 
could  be  removed  for  analysis.  At  the  same  time  the  urine  and 
feces  could  also  be  collected  for  a  complete  chemical  analysis  and 
for  a  determination  of  the  energy  still  contained  in  them.. 

Net  available  energy.  We  have  seen  that  food  is  not  applied 
to  use  until  it  reaches  the  blood.  It  must  have  work  done  upon 
it  before  it  is  in  solution.  The  processes  of  mastication,  of  mov- 
ing it  along  the  digestive  tract,  and  of  bringing  it  into  solution 
all  require  the  expenditure  of  a  certain  amount  of  energy.  Zuntz, 
working  with  a  horse,  has  attempted  to  measure  this.  His  method 
has  been  to  determine  by  various  devices,  how  much  more  oxygen 
is  consumed  during  mastication  and  digestion  than  before  or 
after  these  operations  are  accomplished.  From  this  measure  of 
oxygen  consumption,  he  calculated  the  following  heat  units,  rep- 
resenting the  energy  used  in  chewing  certain  feeds : 

Cal. 

1  pound  corn.  (454  grams) 6.3 

1  pound  oats 21.0 

1  pound  hay  ;<,. o 

(/  This  is  an  important  finding.  Zuntz  calculates  that  in  general 
the  coarse  feeds  have  20  per  cent  less  net  energy  value  than  the 
grains  and  that  the  work  of  mastication  and  digestion  combined 
is  about  48  per  cent  of  the  energy  value  of  the  digested  material 
from  hay  and  19.7  per  cent  of  that  from  oats.  We  must  remem- 
ber, however,  that  the  wastefulness  of  fibrous  foods  shown  in 


Feeding  Standards.  239 

these  determinations  on  the  horse  are  not  true  to  an  equal  extent 
in  the  case  of  ruminants.  In  the  latter  the  fiber  is  softened  in  the 
paunch  and  its  digestion  has  begun  before  it  reaches  the  intestines. 

Net  available  energy  then,  is  the  available  energy  minus  the 
energy  of  digestion  and  preparation  of  the  food  for  use.  This 
internal  work  furnishes  heat,  and  provided  it  is  not  in  excess 
of  the  heat  requirement  of  the  animal,  should  not  be  regarded 
as  waste.  The  waste  of  heat  has  begun  when  that  produced  by 
the  work  of  digestion  exceeds  the  animal  requirement.  But  if  it 
is  produced  in  the  digestive  tract  and  not  in  the  tissues  of  the 
animal,  it  cannot  appear  as  useful  work. 

We  learn  from  this  that  it  is  not  the  total  chemical  energy  in 
a  feeding  stuff  which  measures  its  value  to  the  body,  but  that 
which  remains  after  deducting  the  energy  losses  in  the  unburned 
material  of  the  excreta,  the  energy  expended  in  digesting  the  real 
fuel  materials  from  the  food,  and  in  addition,  the  energy  used  in 
transforming  them  into  substances  which  the  body  can  use  or 
store  up.  This  gives  us  what  Kellner  calls  the  productive  value 
of  feeds,  and  is  identical  in  meaning  with  the  term  net  available 
energy  of  feeds. 

Productive  value  of  feeds.  From  elaborate  experiments  with 
the  respiration  chamber  and  mature  oxen  Kellner  has  determined 
the  productive  value  of  certain  feeds.  For  this  purpose  he  chose 
rather  lean  oxen,  giving  them  a  fixed  moderate  ration  which  re- 
sulted in  a  small  increase  in  weight.  He  then  added  to  the  ration 
the  feed  to  be  experimented  with,  and  determined  the  amount  of 
increase  produced.  This  was  not  done  by  weighing  the  animal, 
but  by  determining  the  amount  of  nitrogen  and  carbon  retained 
by  the  animal.  The  protein  tissue  stored,  was  calculated  from  the 
nitrogen  retained  and  the  fat  from  the  carbon  left  after  deducting 
the  carbon  required  to  build  the  increase  in  protein.  Kellner 's 
results  are  shown  in  the  following  table. 

The  available  energy  of  these  feeds  had  already  been  deter- 
mined and  is  given  in  the  first  column.  In  the  second  column 
appears  the  percentage  of  loss  in  the  process  of  digestion  and 


240 


Agricultural  Chemistry. 


assimilation  and  production  of  tissue.  The  last  two  columns  ex- 
press the  energy  value  of  the  increase  and  the  comparative  pro- 
ductive value  o£  the  different  materials,  with  starch  as  a  unit. 
We  see  from  this  that  56.3  per  cent  of  the  digested  fat  (peanut 
oil)  was  stored,  and  44.7  per  cent  of  the  digested  protein  (wheat 
gluten),  while  but  17.8  per  cent  of  the  digested  wheat  straw  was 
available  for  useful  energy  or  increase.  This  gives  us  a  scien- 
tific explanation  of  the  fact  that  coarse  feeds  are  not  adapted  to 
rapid  production. 

From  such  data  Kellner  concludes  that  1  pound  of  digested 

Heat  Values  of  Digested  Feeds  and  of  the  Increase  Obtained 
in  a  Fattening  Ox. 


Heat  value 
to  the  ox  of 
1  gram  of 
digested 
substance 

Loss  of 
energy  in 
productive 
processes 

Heat  value 
of  increase 
obtained 

Comparative 
productive 
value. 
Starch  100 

Starch  . 

Gate. 
3  7 

Per  cent 
41  1 

Cals. 
2  2 

100 

Molasses         

3  6 

36  4 

2  3 

104 

Straw  pulp  
Wheat  gluten  

3.6 

4-7 

36.9 
55  3 

23 

2.1 

104 
101 

Peanut  oil  .... 

s  g 

43  7 

4  9 

224 

Meadow  hay 

3  6 

58  5 

1  5 

68 

Oat  straw 

3  7 

62  4 

1  4 

64 

Wheat-straw  . 

3  3 

82  2 

1  6 

27 

starch  may  yield  a  maximum  of  0.23  pound  of  body  fat,  the  rest 
being  consumed  in  the  transformation  processes.  Taking  1  pound 
of  digestible  starch  as  his  standard,  he  has  formulated  the  relative 
values  for  the  digestible  nutrients  in  feeding  stuffs,  based  on  the 
amount  of  body  fat  the  several  pure  nutrients  would  form  if  fed 
to  the  ox. 

Kellner's  starch  values.  These  are  the  values  of  the  nutrients 
of  feeds  expressed  with  starch  as  a  unit  of  energy.  From  the 
quantities  of  digestible  nutrients  in  1000  pounds  of  ordinary  feed- 
ing material,  the  relative  value  of  feeds  for  maintenance  and 


Feeding  Standards. 


241 


production  in  terms  of  starch  have  been  calculated  by  Kellner. 
No  extended  table  will  be  given  here.  However,  to  make  this 
clear  the  digestible  nutrients  in  a  few  common  feeding  materials 
are  brought  together  in  the  following  table.  This  table  includes 
the  amides,  which  are  not,  in  American  tables  as  a  rule,  dis- 
tinctly separated,  but  included  under  the  term  "crude  protein'* 
(NX  6.25). 

Pounds  of  Digestible  Matter  in  1000  Pounds  of  Various  Feeds. 


* 

Total 
organic 
matter 

Nitrogenous  Substances 

Fat 

Garb. 

Fiber 

Protein 

Amides 

Corn          

786 
600 
715 
440 
381 
351 

?3 

81 
70 

47 

i 

* 

(5 

7 
4 
25 
5 

[  ' 

44 
45 
19 
13 
7 
4 

651 
441 
607 
269 
163 
150 

12 
26 
15 
151 
199 
193 

Oats         

Barley      .         .... 

Clover  hay  

Oat  straw  

Wheat  straw  

From  these  data  the  maintenance  value  in  terms  of  starch  is 
made  by  the  simple  calculation: — Protein  X  1-25  1  +  Amides  X 
0.6  +  Fat  X  2.3  +  Garb.  +  Fiber. 

From  this  we  see  that  the  feeds  for  maintenance  are  valued  at 
the  full  heat  value  of  the  digestible  constituents.  The  heat  which 
is  the  final  outcome  of  the  mechanical  labor  employed  in  digestion, 
can  serve  for  warming  the  animal.  But  when  the  productive 
value  is  considered,  it  has  been  found  that  if  we  take  only  the 
digestible  fat,  protein,  and  carbohydrates  of  the  ration,  and  give 
to  each  the  energy  value  found  for  it  in  Kellner 's  production  ex- 
periments, the  sum  of  these  will  approximate  the  values  actually 
obtained  in  the  experiments  tried.  Consequently  the  productive 
value  in  terms  of  starch  =  Fat  X  2.3  +  Protein  +  Garb. 

lThe  factors  1.25,  0  6,  and  2.3  are  those  in  use  in  Europe  for  converting 
the  food  constituents  to  an  energy  basis  equivalent  to  starch.  It  should  be 
observed  that  generally  the  factor  2.4  for  fat  is  the  only  one  used. 


142 


Agricultural  Chemistry. 


In  the  following  table  are  assembled  a  few  examples  of  the 
starch  equivalents  of  feeds  for  both  maintenance  and  production, 
as  formulated  by  Kellner. 

Comparative  Value  of  Ordinary  Feeds  for  Oxen  and  Sheep. 


For  Maintenance 

For  Production 

Value  of 
1000  Ibs.  as 
starch 

Quantities 
equivalent 
to  1  Ib.  of 
starch 

Value  of 
1000  Ibs.  as 
starch 

Quantities 
equivalent 
to  1  Ib.  of 
starch 

Corn          

859 
676 
755 
459 
412 
357 

1.18 

1.48 
1.32 
'2.18 

2.43 
2.80 

825 
626 
721 
319 
207 
96 

1.21 
1.6€ 
1.39 
3  13 
4.83 
10.41 

Oats  

Barley  

Ciover  hay  

O  it  straw  

Wheat  straw  ...    . 

Kellner  admits  that  our  knowledge  of  the  actual  productive 
value  of  feeds  is  still  very  incomplete.  Such  values  have  been 
determined  by  actual  experiments  in  only  a  few  cases  and  then 
only  for  the  mature  fattening  ox.  It  serves,  however,  to  illus- 
trate the  trend  of  experimentation  and  the  serious  and  laborious 
attempts  being  made  to  place  the  nutritive  value  of  feeding  stuffs 
on  a  scientific  experimental  basis.  It  appears  from  the  above 
table  that  approximately  2  pounds  of  oat  or  wheat  straw  may 
replace  1  pound  of  corn,  if  the  ox  or  sheep  is  merely  on  a  main- 
tenance diet,  but  that  1  pound  of  corn  will  have  as  great  an  effect 
as  4  pounds  of  oat  straw  or  10  pounds  of  wheat  straw  when  the 
animal  must  grow  or  fatten. 

Kellner's  feeding  standards.  The  first  table  on  the  following 
page  is  a  brief  summary  of  these  standards. 

Armsby's  feeding  standards.  As  an  outgrowth  of  tho  work 
of  Kellner  and  continued  work  with  the  respiration  calorimeter, 
Armbsy  has  begun  to  formulate  feeding  standards,  giving  the  net 
productive  energy  of  feeding  stuffs.  These  are  expressed  in 


Feeding  Standards. 
Standard  Rations  for  1000  Lbs.  of  Farm  Animals. 


243 


, 

Drv 

Digestible 

Nutrients 

matter 

Proteins 

Starch  value 

Maintenance  of  mature  steers  

Lbs. 

15-21 

Lbs. 
0.6 

Lbs. 
6.0 

Fati  ening  steers  

24-32 

1.5-1.7 

12.5-14.5 

Milch  cow  giving  20  Ibs.  milk  daily.  .  . 
Milch  cow  giving  30  Ibs.  milk  daily.  .  . 
Horse  at.  light  work  

25-29 
27-33 

18-25 

1.6-1.9 
2.2-2.5 
1.0 

9.8-11.2 
11.8-13.9 
9.2 

Hor^e  at  heavy  work 

23-29 

2  0 

15  0 

Fattening  swine  1st  period  

33-37 

3.0 

27.5 

Fattenin0"  swine  2nd  period.         

28-33 

2.8 

26.1 

Fattening  swine  3rd  period  

24-28 

2.0 

19.8 

therms,  and  for  illustration  several  examples  are  brought  together 
in  the  following  table.  The  complete  table  will  be  found  in  the 
appendix. 

Dry  Matter,  Digestible  Protein  and  Energy  Value  in  100  Lbs. 


Feeding  stuff 

Total 
dry  matter 

Digestible 
protein 

Energy  value 

Green  alfalfa 

Lbs. 
28  2 

Lbs. 
2  50 

Therms 
12  45 

Drv  alfalfa  

91.6 

6.93 

34.41 

Oat  straw  

90.8 

1.09 

21.21 

Corn    meal 

89  1 

6  79 

88  84 

Wheat  bran 

88  1 

10  21 

48  23 

The  table  is  supposed  to  represent,  with  a  fair  degree  of  ac- 
curacy, the  digestible  protein  and  the  net  energy  which  the  various 
feeding  stuffs  will  supply.  They  express  what  is  available  to  the 
animal  for  growth,  fattening,  work  or  milk  production,  after  de- 
ducting that  used  in  the  work  of  mastication  and  assimilation. 
The  digestible  protein  in  the  table  is  true  protein  and  does  not 
include  the  so-called  "amides"  of  the  "crude  protein." 


244 


Agricultural  Chemistry. 


Standards  for  maintenance.  The  following  table  shows  the 
amount  of  digestible  protein  and  net  energy  required  per  head 
for  the  maintenance  of  cattle,  sheep  and  horses  of  different 
weights.  No  figures  for  swine  are  available. 

Arm^by's  Maintenance  Standards  for  Horses,  Cattle  and  Sheep. 


Horses 

Cattle 

Sheep 

Live 
weight 

Digest- 
ible 

Energy 

Digest- 
ible 

Energy 

Live 
weight 

Digest- 
ible 

Energy 

protein 

value 

protein 

value 

protein 

value 

Lbs. 

Lbg. 

Therms 

Lbs. 

Therms 

Lbs. 

Lbs. 

Therms 

150 

.15 

1.70 

.30 

2.00 

20 

.02 

.  30 

250 

.20 

2.40 

.40 

2.80 

40 

.05 

.54 

500 

.30 

3.80 

.60 

4.40 

60 

.07 

.71 

750 

.40 

4.95 

.80 

5.80 

80 

.09 

.87 

1000 

.50 

6.00 

1.00 

7.00 

100 

.10 

1.00 

1250 

.60 

7.00 

1.20 

8.15 

120 

.11 

1.13 

1500 

.65 

7.90 

1.30 

9.20 

140 

.13 

1.25 

Prom  the  table  one  sees  that  a  colt  of  500  Ibs.  weight  will  re- 
quire for  daily  support.  0.3  Ib.  of  digestible  protein  and  3.8 
therms,  while  when  it  has  trebled  its  weight  the  requirements  are 
0.65  Ib.  of  digestible  protein  and  7.9  therms.  In  other  words  the 
requirements  have  not  increased  in  proportion  to  the  gain  in 
weight. 

Standards  for  growing  animals.  The  following  table  gives 
the  digestible  protein  and  energy  required  for  growing  cattle  and 
sheep,  as  set  forth  by  Armsby.  No  data  for  horses  and  swine  are 
available.  The  table  includes  the  maintenance  requirement. 

The  table  shows  that  a  six  months  old  calf,  weighing  425  pounds 
requires  1.3  pounds  of  digestible  protein  and  6  therms  of  energy 
value,  which  includes  the  1.3  pounds  of  protein.  Where  the  calf 
has  grown  to  weigh  1100  pounds,  or  more  than  doubled  its  weight, 
it  requires  0.35  pound  more  protein  and  2  more  therms.  This 
relative  lessening  in  feed  required  is  due  to  the  fact  that  a  larger 


Feeding  Standards. 


245 


animal  requires  relatively  less  for  maintenance,  and  to  the  addi- 
tional fact  that  the  rate  of  growth  has  greatly  decreased.  Armsby 
allows  1.75  pounds  of  digestible  protein  for  a  steer  weighing 
1000  pounds,  while  but  1.65  is  required  when  the  same  steer 
reaches  1100  pounds.  This  is  due  to  the  lessened  increase  in 
muscular  tissue  and  consequently  decreased  demand  for  protein 
food,  as  compared  with  the  earlier  stages  of  life.  It  should  be 
noted  that  in  comparing  maintenance  and  growing  requirements, 
the  larger  part  o£  all  the  food  consumed  is  used  for  body  support, 
and  that  additional  requirements  for  growth  are  mainly  in  pro- 
tein, rather  than  therm  requirements. 

Armsby's  Standards  for  Growing  Cattle  and  Sheep. 


Cattle 

Sheep 

Age 

Live 
weight 

Digest- 
ible 
protein 

Energy 
value 

Live 

weight 

Digest- 
ible 
protein 

Energy 
value 

Months 
3                       

Lbs. 
275 

Lbs. 
1.10 

Therms 
5.0 

Lbs. 

Lbs. 

Therms 

6                

425 

1.30 

6.0 

70 

.30 

1.30 

9 

90 

.25 

1  .40 

12         .    .           

650 

1.65 

7.0 

110 

.23 

1.40 

15 

130 

.23 

1.50 

18  

850 

1.70 

7.5 

145 

.22 

1.60 

24  
30  

1000 
1100 

1.75 
1.65 

<s.o 

8.0 

Standards  for  milch  cows  and  fattening  steers.     In  addition 
to  the  foregoing  standards,  Armsby  recommends  the  following : 

1.  For  milk  production  add  to  the  maintenance  standard  0.05 
pound  of  digestible  protein  and  0.3  therm  for  each  pound  of 
average  milk  containing  13  per  cent  of  total  solids  and  4  per  cent 
of  fat. 

2.  For  fairly  mature  fattening  cattle  add  3.5  therms  to  the 
maintenance  standard  for  each  pound  of  gain  in  live  weight. 

Armsby  does  not  provide  additional  protein  to  the  maintenance 
standard  for  fattening  steers,  holding  that  if  the  proper  allow- 


246 


Agricultural  Chemistry. 


ance  of  therms  is  provided  in  addition  to  the  maintenance  ration, 
no  additional  protein  is  required  for  fattening  purposes.  On  the 
other  hand,  for  milk  production  the  standard  provides  additional 
protein.  This  must  be  done  because  of  the  protein  content  of 
the  milk  itself  and  the  additional  factor  of  protein  supply  for 
the  developing  foetus. 

3.  Armsby  recommends  that  a  1000  pound  ruminant  should 
be  given  from  20  to  30  pounds  of  dry  matter  per  day,  while  for 
the  horse  smaller  amounts  can  be  used. 

Standard  for  the  working  animal.  The  horse  is  the  only  ani- 
mal to  be  considered  here.  What  applies  to  the  horse  may  also 
be  used  for  the  mule.  As  a  general  average,  Kellner  recommends 
the  following  ration  for  a  1000  pound  horse,  the  amounts  stated 
including  the  maintenance  requirement: — 

Requirements  of  the  Working  Horse. 


Digestible  protein 

Energy  value 

For  light  work                

Lbs. 
1  0 

Therms 

9.80 

For  medium  work         

1.4 

12.40 

I1  or  heavy  work  

2  0 

16.00 

Future  of  standards.  The  feeding  standards  being  developed 
at  the  present  time  are  in  a  formative  stage,  and  necessarily  in- 
complete. No  standard  should  be  used  as  an  exact  mathematical 
expression  of  the  animal 's  needs.  In  fact  it  cannot  be  done,  be- 
cause we  are  not  in  a  position  to  know  the  exact  requirements  of 
the  individual  animal;  again,  feeding  stuffs  of  the  same  namt 
show  a  considerable  range  in  composition.  Further,  probably  th( 
most  important  factor  in  limiting  the  adoption  of  a  feeding 
standard  as  a  final  recipe  in  feeding,  is  the  difference  in  nutritive 
value  and  physiological  action  of  the  nutrients  from  varioi 
sources.  One  species  of  farm  animal  may  do  better  on  the  nu- 
trients from  one  specific  source,  as  compared  with  those  derived 


Feeding  Standards.  247 

from  another.  In  addition,  the  relative  amounts  and  kinds  of 
ash  must  be  considered.  The  value  of  wheat  bran  does  not  re- 
side wholly  in  its  protein  content,  but  partly  in  its  laxative  prop- 
erties, which  are  due  to  a  specific  constituent,  known  as  phytin. 
The  superior  value  of  legume  hays  must  be  attributed,  in  part,  to 
their  high  lime  content.  This  is  particularly  true  when  used  for 
growing  animals  and  milch  cows.  All  these  are  factors  to  be 
reckoned  with,  but  until  they  are  completely  worked  out  and 
catalogued,  the  student  will  still  find  the  standards  of  Wolff  or 
Armsby  helpful  in  formulating  rations. 


CHAPTER  XI 
FOOD  REQUIREMENTS  OF  ANIMALS. 

The  young  growing  animal.  The  distinct  and  characteristic 
feature  of  the  growth  of  young  animals  is  the  rapid  formation 
of  soft  tissue  and  bone.  For  this  purpose  there  must  be  an 
abundant  supply  of  protein  and  suitable  ash. 

This  is  true  for  all  young  domestic  animals.  The  daily  in- 
crease in  live  weight  of  a  well  nourished  calf  is  very  considerable 
and  may  be  as  large  as  that  of  a  well-fed,  mature  steer.  It  may 
amount  to  2  pounds  per  day ;  and  much  less  than  this  would  be 
regarded  as  unsatisfactory.  Lawes  and  Gilbert  analyzed  the 
entire  body  of  a  fat  calf  with  the  following  results: — 

Per  cent 

Water 64.6 

Ash 4.8 

Protein 16.  * 

Fat 14.1 

Based  on  this  analysis  the  daily  increase  of  2  pounds  live  weight 
in  a  growing  calf  would  mean  a  storage  of  about  0.33  Ib.  of  pro- 
tein and  0.28  Ib.  of  actual  fat,  or  a  total  increase  of  0.61  Ib.  of 
dry  body  material.  This  may  be  equal  to  one-fifth  or  more  of 
the  total  dry  substance  of  the  ration.  European  investigations 
with  calves  have  shown  that  one  pound  of  milk  solids,  practically 
all  digestible,  produced  one  pound  of  increase  in  live  weight.  Be- 
cause of  the  water  content  of  this  increase,  the  actual  dry  matter 
is  equal  to  about  one-third  of  a  pound.  Further,  these  studies 
showed  that  70  per  cent  of  the  protein  of  the  food  was  retained 
in  the  bodies  of  the  calves  and  72  per  cent  of  the  phosphoric  acid 
and  97  per  cent  of  the  lime  held  for  skeleton  and  tissue  expansion. 
On  an  assumed  consumption  of  10  pounds  of  average  milk  daily, 
this  would  mean  a  retention  of  6.4  grams  (approximately  one- 
fifth  of  an  ounce)  of  phosphoric  acid  and  8.7  grams  of  lime. 


Food  Requirements  of  Animals. 


249 


In  this  country,  experiments  with  young  lambs  fed  cow's  milk 
showed  a  gain  in  live  weight  of  one  pound  for  every  5.8  pounds 
of  milk  consumed.  If  the  milk  contained  13  per  cent  of  dry 
matter,  then  0.75  pound  of  milk  solids  produced  1  pound  of  in- 
crease. This  is  a  high  food  efficiency  and  practicaUy  ten  times 
that  shown  with  animals  somewhat  mature.  This  serves  to  il- 
lustrate the  rapid  increase  in  tissue  during  the  early  periods  of 
growth. 

The  kind  of  food  most  appropriate  to  the  wants  of  the  young 
animal  is  revealed  by  the  composition  of  milk.  The  first  milk 
secreted  by  the  mother  (colostrum)  is  very  rich  in  protein,  often 
containing  as  high  as  15  per  cent.  This  gradually  changes  after 
parturition  and  after  a  lapse  of  8  to  10  days  the  composition  of 
the  secretion  becomes  normal.  Below  is  given  the  composition  of 
colostrum  and  the  normal  milk  of  our  common  farm  animals. 

Percentage  Composition  of  Colostrum  Milk. 


Nu- 

Water 

Protein 

Fat 

Sugar 

Ash 

tritive 

ratio 

Ewe            .     . 

66.4 

16.6 

10.8 

5  0 

I  2 

1-1  8 

Sow         .           

70.1 

15.6 

9.5 

3.8 

0  9 

1-1  6 

Cow      

74.7 

17.6 

3.6 

2.6 

1  5 

1*0  6 

Percentage  Composition  of  Milk. 


Ewe  

80.8 

4.9 

6.9 

4.9 

.84 

1-3.1 

Sow 

84  6 

5  2 

4  8 

3  2 

80 

1-92 

Cow 

87.0 

3.5 

3  9 

4  8 

70 

1-37 

]V1  a^ 

90  8 

2  0 

1  2 

5  6 

40 

1-39 

The  solid  matter  of  milk  has  a  high  feeding  value,  because  of 
its  complete  utilization  by  the  animal.  It  also  supplies  an  abun- 
dant amount  of  ash  material  for  skeleton  and  tissue  formation. 
That  each  species  has  provided  for  the  young  a  milk  of  such  pro- 


250  Agricultural  Chemistry. 

tein  and  ash  content  as  will  meet  the  rate  of  development  char- 
acteristic for  that  species  is  seen  in  the  following  table: — 

Days  required 
Protein  Ash  to  double  weight 

E\ve 4.9  per  cent  0.84  per  cent  15 

Sow    5.2    "     "  0.80    "     "  14 

Cow 3.5    "     "  0.70    "     "  47 

Mare 2.0    "     "  0.40    "     ."  (i() 

Human 1.6    "     "  0.20    "     "  ISO 

This  is  a  very  suggestive  relation  of  the  protein  and  ash  content 
of  milk  to  the  rate  of  growth  and  serves  to  illustrate  the  necessity 
of  maintaining  a  liberal  supply  of  these  materials  in  easily  avail- 
able form  for  the  growing  young.  It  is  also  necessary  to  remem- 
ber that  approximately  50  per  cent  of  the  ash  of  milk  is  made 
up  of  the  bone-forming  constituents,  lime  and  phosphoric  acid. 
This  emphasizes  the  desirability  of  maintaining  the  supply  of 
these  ash  constituents  in  the  feed  of  the  animal  as  the  mother's 
milk  is  withdrawn  and  other  feeds  substituted. 

Supply  of  ash  material  necessary.  Probably  no  class  of  farm 
animals  is  exposed  to  as  much  danger  in  this  regard  as  the  pig. 
Abundant  supplies  of  lime,  in  particular,  are  contained  in  the 
hays  and  leafy  parts  of  plants,  but  these,  normally,  do  not  form 
a  part  of  the  ration  of  this  species  of  farm  animals.  The  grains 
are  low  in  lime;  and  even  wheat  bran,  so  often  accredited  with 
abundant  bone  forming  materials,  is  relatively  low  in  lime.  It 
contains  an  abundant  supply  of  phosphorus,  and  in  so  far  as 
the  supply  of  this  element  is  concerned,  normal  rations  for  all 
classes  of  farm  animals,  of  which  the  grains  and  particularly 
wheat  bran  form  a  part,  will  generally  supply  a  sufficient  quan- 
tity. In  furnishing  an  abundant  natural  supply  of  lime  to  the 
growing  animal,  recourse  may  be  had  to  the  legume  hays  for 
ruminants  or  the  ground  meal  from  alfalfa  or  clover  hay  for  the 
young  pig. 

The  meadow  hays  are  also  rich  in  lime,  but  do  not  contain  as 


Food  Requirements  of  Animals.  251 

much  as  the  legume  hays.  The  beneficial  use  of  wood  ashes,  as 
a  supplement  to  corn  in  the  ration  of  pigs,  probably  lies,  in  part 
at  least,  in  its  high  lime  content.  The  use  of  artificial  sources  of 
lime  for  growing  animals  of  all  classes,  where  the  natural  sources 
are  not  available,  is  highly  justifiable.  Probably  lime  as  a  phos- 
phate  serves  this  purpose  best,  and  either  what  is  called  pre- 
cipitated calcium  phosphate  or  the  crude,  finely  ground  phosphate 
known  as  ''floats"  can  be  used  to  advantage.  About  14  "to  %  of 
an  ounce  per  100  pounds  of  live  weight  during  the  rapidly  grow- 
ing periods  should  serve  the  purpose  of  building  a  strong  skeleton. 


The  effect  of  improperly  balanced  rations  on  growing  animals.     The  ra- 
tion fed  these  pigs  was  too  low  in  phosphorus. 

No  attempt  is  made  here  to  give  directions  for  feeding  animals : 
this  must  be  sought  for  in  texts  wholly  devoted  to  that  subject. 
Only  a  few  of  the  more  fundamental  principles  are  discussed. 

Dangers  from  too  rich  milk.  In  recognizing  the  mother's  milk 
as  supplying  the  nutrients  in  the  best  forms  and  proportions,  it 
is  necessary  to  add  that  milks  very  rich  in  fat  have  been  found 
to  cause  intestinal  disturbances  and  impaired  nutrition.  This  is 
not  only  true  of  cow's  milk  fed  the  calf,  but  also  true  when  that 
milk  is  fed  to  pigs  or  to  the  human  infant. 

The  following  explanation  for  this  harmful  effect  of  excess  of 
fat  in  the  food  has  been  offered: — The  general  capacity  of  an 
organism  for  the  absorption  of  fat  is  strictly  confined  within  nar- 
row limits  and  consequently  an  excessive  supply  is  not  absorbed. 


252  Agricultural  Chemistry. 

but  remains  in  the  intestine.  There  it  is  converted  into  soaps, 
composed  of  part  of  the  fat  and  an  alkali,  and  as  such  eliminated 
from  the  body  in  the  excreta.  This  excretion  of  soap  entails  to 
the  body  a  heavy  loss  of  alkaline  bases,  which  when  continued  for 
some  time  results  in  disturbed  nutrition.  On  an  exclusive  milk 
diet  containing  3.5  per  cent  of  fat  the  supply  of  alkaline  bases  i? 
only  sufficient  for  normal  development  and  the  production  of  fat- 
rich  milk  in  cows  is  not  attended  by  a  corresponding  increase  in 
the  ash  forming  materials.  Rich  milk  is  the  result  of  breeding 
by  man  and  is  not  a  condition  original  to  the  milk  of  the  cow. 

Another  important  fact  to  bear  in  mind  is  that  the  capacity  to 
digest  the  starchy  grains  and  similar  substances  is  somewhat  un- 
developed in  the  very  young  animal  and  that  the  ferments  neces- 
sary for  this  purpose  are  probably  not  yet  very  abundant.  For 
this  reason  the  first  substitute  for  milk  should  not  consist  too 
largely  of  cereal  grains,  or  concoctions  of  insoluble,  starchy  ma- 
terials. Bulky,  fibrous  food  is  likewise  unsuitable  for  the  young 
animal.  The  digestive  tract  of  calves  and  colts  must  gradually 
expand  before  the  coarse  hays  can  form  a  large  part  of  their  ra- 
tion. 

Influence  of  food.  In  experiments  on  the  influence  of  food 
upon  the  development  of  the  animal  body,  some  interesting  results 
have  been  recorded.  Sanborn  and  Henry  fed  to  swine  rations 
varying  considerably  in  the  protein  and  ash  supply.  Comparisons 
of  middlings  and  blood  against  corn  meal  alone,  or  shorts  and  bran 
against  potatoes,  tallow  and  corn  meal,  showed  considerable  dif- 
ferences in  the  development  of  the  animal.  Those  fed  high  nitro- 
genous rations  contained  more  blood  than  the  others,  while  such 
organs  as  the  kidney  and  liver  were  larger  in  proportion  to  the 
weight  of  the  body,  the  bones  stronger,  and  the  proportion  of 
muscle  greater.  These  were  extreme  rations,  and  not  likely  to 
occur  in  practice,  but  the  experiment  serves  the  purpose  of  em- 
phasizing the  necessity  of  an  abundant  supply  of  protein  and  ash 
material  for  the  growing  young.  Swine  fed  on  corn  and  gluten 
feed,  against  corn,  gluten  feed  and  "floats"  have  shown  marked 


Food  Requirements  of  Animals.  253 

differences  in  the  skeleton  development.  In  this  experiment  the 
proteins  were  abundantly  supplied  in  both  rations,  but  only  in  the 
second  was  there  a  liberal  supply  of  lime  and  phosphoric  acid. 
Where  such  a  supply  was  maintained  the  skeletons  were  large 
and  strong. 

Jordan  fed  two  lots  of  steers  from  calf -hood  on  rations  widely 
different  in  their  nutritive  ratio.  The  one  lot  received  for  grain, 
oil  meal,  wheat  bran  and  corn  meal,  and  the  other  lot  corn  meal, 
with  a  minimum  proportion  of  wheat  bran.  A  nutritive  ratio  of 
1 :5.2  and  1 :9.7  was  maintained.  At  the  end  of  17  months  and 
27  months,  one  animal  from  each  lot  was  killed  and  the  entire 
body,  exclusive  of  hide,  analyzed.  There  was  no  material  differ- 
ence in  the  composition  of  the  animals.  ' '  The  amount  of  growth 
was  at  first  more  rapid  with  the  more  nitrogenous  ration,  but  the 
kind  of  growth  appeared  to  have  been  controlled  by  the  somewhat 
fixed  constitutional  habits  of  the  breed. "  (Jordan.) 

It  is  sometimes  claimed  by  practical  men  that  feeds  rich  in  bone- 
forming  materials  should  be  withheld  from  the  pregnant  mother ; 
that  such  feeds  are  conducive  to  large  boned  offspring,  making  it 
difficult  for  the  young  to  be  born.  Little  data  on  this  question 
are  available,  but  from  some  experiments  on  swine  at  the  Wis- 
consin Station,  there  is  no  evidence  that  excessive  supplies  of  bone- 
forming  materials  influence  the  size  or  the  ash  content  of  the 
skeleton  of  the  newly  born.  It  appears  that  the  power  to  main- 
tain a  constant  composition  for  the  foetus,  independent  of  wide 
variations  in  food  supply,  lies  inherent  in  the  mother. 

The  adult  animal  and  food  for  maintenance.  The  food  of  an 
adult  animal,  neither  gaining  nor  losing  in  weight,  is  used  for 
renewal  of  waste  tissue,  the  growth  of  hair,  horn  and  wool,  and 
for  the  production  of  heat  and  mechanical  work.  The  work  per- 
formed consists  in  the  muscular  movements  involved  in  chewing 
and  moving  the  food  along  the  intestinal  tract;  muscular  move- 
ments of  the  heart  in  pumping  the  blood;  respiration  and  the 
metabolic  activity  of  the  cells  in  causing  the  chemical  transforma- 
tions of  the  nutrients.  This  is  internal  work.  It  has  been  cal- 


254 


Agricultural  Chemistry. 


culated  that  the  power  exerted  daily  by  the  heart  of  a  man  150  Ibs. 
in  weight,  would  raise  1  ton  to  a  height  of  242  feet.  Then  in  ad- 
dition, there  is  always  some  work  done  in  moving  the  body  from 
place  to  place.  A  horse  of  1100  pounds  weight,  walking  20  miles 
on  level  ground,  and  without  a  load,  will  do  work  equivalent  to 
raising  2328  tons  1  foot.  The  internal  work  finally  appears 
largely  as  heat,  while  in  the  external  movements  of  the  body, 
probably  70  per  cent  of  the  total  energy  developed  in  the  muscles 
appears  as  heat. 

The  smaller  the  animal  the  greater  the  loss  of  heat  per  unit  of 
weight,  and  consequently  the  more  liberal  must  be  the  supply  of 
food.  This  is  because  small  bodies  have  in  proportion  to  their 
weight,  a  much  greater  surface.  Thus,  heat  is  lost  by  radiation 
from  the  surface  of  the  body  and  in  evaporating  the  water  ex- 
haled through  the  lungs  and  skin. 

In  the  following  table  the  heat  production  in  resting  animals 
is  given: — 

Heat  Production  in  Resting  Animals. 


Weight 
in  pounds 

Calories  produced 

Per  pound 

Per  sq.  mm. 
surface 

Horse  

970.0 
281.0 
33  0 
7.7 
0.03 

24.8 
42.0 
103.0 
146.7 
466.0 

948 
1078 
IO&) 
943 

917 

Pig 

Doe 

Goose  .... 

Mouse 

This  shows  that  animals  will  produce  heat  in  proportion  to 
their  surface ;  it  is  interesting  to  note  that  in  the  standard  rations 
for  animals,  the  quantity  of  food  increases  at  nearly  the  same 
ratio  as  the  surface  increases.  For  example,  while  the  oxen  in 
growing  from  a  weight  of  165  to  935  pounds  increases  in  weight 
5.7  times,  the  surface  of  the  animal  increases  but  3.2  times  and 
the  food  required,  3.5  times. 


Food  Requirements  of  Animals.  255 

It  is  essential  that  the  maintenance  ration  should  supply  enough 
protein  to  replace  the  daily  waste  of  the  nitrogenous  tissue.  Only 
a  small  amount  is  necessarily  destroyed  by  the  resting  animal; 
but  there  is  a  constant  waste,  and  unless  this  is  replaced  the 
animal  will  die  of  starvation.  It  is  plain  then  that  the  demands 
upon  food  for  maintenance  purposes  are  mainly  for  the  produc- 
tion of  muscular  energy  and  heat.  Armsby  found  that  a  supply 
of  0.6  Ib.  of  digestible  protein  per  day  was  sufficient  for  the 
permanent  maintenance  of  a  1000  pound  ox,  receiving  a  ration 
with  a  nutritive  ratio  of  1:11. 

The  thorough  studies  of  Zuntz  on  the  horse  have  shown  that  a 
1000  pound  animal  can  be  maintained  on  6.4  pounds  of  available 
nutrients,  provided  the  total  ration  does  not  contain  more  than 
three  pounds  of  crude  fiber.  This  means  that  the  nutrients  must 
come  from  hay  and  grain.  Grandeau  places  ths  maintenance  re- 
quirement for  the  same  weight  of  animal  at  7  to  7.8  pounds  of 
digestible  organic  matter,  including  0.45  pound  of  digestible  pro- 
tein. 

There  are  few  experiments  with  sheep,  but  according  to  German 
experiments,  13.8  pounds  of  digestible  organic  matter,  including 
1.0  pound  of  digestible  protein,  per  3000  pounds  live  weight  are 
required  to  maintain  proper  conditions.  Its  continued  produc- 
tion of  wool,  higher  temperature  and  smaller  size  make  the  re- 
quirements for  this  animal  somewhat  more  liberal  than  with  the 
horse  or  ox. 

It  is  clear  then  that  90  per  cent  or  more  of  a  maintenance  ration 
may  consist  of  carbohydrates  or  materials  used  solely  for  fuel. 
This  makes  it  easy  to  supply  this  ration  from  the  home  grown 
products.  The  quantity  of  available  nutrients  consumed  is  small 
and  may  largely  be  made  up  of  coarse  material,  such  as  corn 
fodder  and  hay.  Again,  the  low  protein  requirement  and  the  pos- 
sibility of  a  wide  nutritive  ratio,  characteristic  of  home  grown 
products,  makes  its  selection  easy. 

Requirements  for  labor.  As  the  horse  is  practically  the  only 
animal  used  in  this  country  for  draft  and  road  purposes,  it  will 


256  Agricultural  Chemistry. 

be  considoivd  alone  in  Ibis  connection.  The  source  of  the  energy 
evolved  during  labor  and  appearing  as  extra  work  and  heat  must 
come  from  the  oxidation  of  food.  If  work  is  to  be  performed 
and  at  the  same  time  body  weight  remain  constant,  the  quantity 
of  food  must  be  increased. 

It  was  supposed  at  one  time  that  muscular  effort  was  produced 
by  the  oxidation  of  the  nitrogenous  constituents  of  the  muscle, 
and  that  a  ration  very  rich  in  protein  was  necessary,  if  hard  work 
was  to  be  maintained.  This  idea  is  now  known  to  be  erroneous. 
Men  have  climbed  mountains  and  measured  the  excretion  of  urea 
(the  principal  nitrogenous  constituent  of  the  urine)  during  such 
severe  exercise.  There  was  no  important  increase  in  its  produc- 
tion under  such  conditions.  Increased  work  increases  the  excre- 
tion of  carbon  dioxide  but  not  of  nitrogen.  In  other  words,  the 
carbohydrates  and  fats  are  largely  the  fuel  materials  that  furnish 
energy  for  mechanical  purposes. 

Zuntz  has  determined  the  quantity  of  food  which  a  horse  needs 
in  order  to  perform  work  under  varying  conditions.  "A  horse 
weighing  with  harness  1144  pounds,  will  require  1.33  pounds  of 
available  food  to  walk  10  miles  at  2%  miles  per  hour ;  1.69  pounds 
when  walking  the  same  distance  at  a  speed  of  3  1/3  miles  per 
hour ;  and  2.53  pounds  when  trotting  the  same  distance  at  7  miles 
an  hour. ' '  This  is  important  knowledge  on  the  influence  of  speed 
upon  the  food  requirement  in  a  unit  of  time. 

The  pace  of  the  animal  is  another  important  factor.  Grandean 
and  Leclerc  kept  a  horse  in  good  condition,  walking  12%  miles 
a  day  with  a  daily  ration  of  19.4  pounds  of  hay,  but  when  thf 
same  distance  was  done  trotting,  24  pounds  was  insufficient.  A 
horse  walking  the  above  distance  and  hauling^  a  load  (equivaleul 
in  additional  work  to  1943  foot-tons)  was  maintained  by  a  ration 
of  26.4  pounds  of  hay ;  but  when  the  same  work  was  done  trotting, 
a  daily  ration  of  32.6  pounds  of  hay,  which  was  all  it  would  eat 
was  insufficient  to  maintain  weight.  Trotting  or  galloping  in- 
volves additional  internal  work;  the  animal  also  lifts  its  own 
weight  at  each  step,  which  only  appears  as  heat  as  it  falls  bacfc 


Food  Requirements  of  Animals.  257 

again.  Consequently  horses  of  different  " action"  will  require 
unlike  amounts  of  food  to  accomplish  the  same  task. 

When  a  horse  exerts  itself  to  the  utmost  the  consumption  of 
oxygen  rises  rapidly  and  the  food  consumed  per  unit  of  work  may 
be  nearly  twice  as  much  as  with  ordinary  draft.  A  slow  pace, 
consistent  with  conditions  involved,  will  be  economical  of  food 
consumption  per  unit  of  work  performed. 

Zuntz  found  that  the  requirements  for  a  horse,  plowing  8  hours 
a  day,  were  14.03  pounds  of  digestible  nutrients.  This  is  some- 
what less  than  the  requirement  found  in  the  German  standards  of 
Wolff  and  Lehmann.  According  to  these  formulas,  a  1000  pound 
horse  requires  11.4  pounds  of  digestible  food  daily  for  moderate 
work,  13.6  pounds  for  average  work,  and  16.6  pounds  for  heavy 
work.  These  standards  also  call  for  a  nutritive  ratio  of  1 :7  to 
1 :6,  dependent  upon  the  severity  of  the  labor.  On  the  other 
hand,  Lavalard,  recommends  that  1.15  pounds  of  digestible  pro- 
tein daily  is  sufficient  for  ordinary  labor,  and  1.35  pounds  when 
the  labor  is  severe.  This  is  a  nutritive  ratio  not  far  from  1 :10. 
From  what  has  been  said  on  the  source  of  muscular  force,  it  is 
probable  that  the  nutritive  ratio  recommended  by  the  German 
standard  is  narrower  than  need  be.  Horses  working  on  the  sugar 
plantations  of  the  Fiji  islands  receive  15  pounds  of  molasses  per 
day  and  a  nutritive  ratio  of  1 :11.8.  However,  a  fairly  good  pro- 
portion of  protein,  for  its  peculiar  and  characteristic  dynamic 
effect,  appears  advisable. 

It  is  the  opinion  of  Jordan  that  ' '  rations  properly  compounded 
from  ordinary  farm  products,  such  as  silage,  roots,  meadow  hay, 
legume  hays  and  the  cereal  grains,  will  generally  contain  protein 
in  sufficient  proportion  and  will  seldom  need  reinforcing  with  the 
commercial  nitrogenous  feeding  stuffs.'* 

If  a  horse  at  severe  labor  requires  16.6  pounds  of  digestible 
nutrients,  it  is  manifest  that  this  could  not  be  obtained  from  the 
coarse  fodders.  Concentrated  feeds  must  be  used.  Ten  pounds 
of  hay  is  all  a  work  horse  should  consume  in  one  day.  We  have 
seen  that  the  productive  value  of  the  coarse  feeds  is  not  as  large 


Agricultural  Chemistry. 

as  the  grains,  and  consequently  cannot  be  expected  to  furnish 
available  energy  for  severe  labor  in  sufficient  quantity,  compatible 
with  the  storage  capacity  of  the  digestive  apparatus  of  the  horse. 

There  has  been  a  strongly  established  opinion  that  oats  are 
pre-eminently  the  horse  feed  and  must  form  a  generous  propor- 
tion of  the  grain  ration;  that  they  give  life  and  nerve  to  the 
animal.  At  one  time  the  discovery  of  a  special  compound, 
"Avenin,"  resident  in  the  oat  kernel  and  endowed  with  these 
stimulating  properties,  was  announced.  This  is  now  disproved 
and  it  is  becoming  more  and  more  evident  that  other  grains  can  be 
substituted  for  oats  with  no  impairment  to  the  animal's  well 
being. 

Fattening  requirements.  To  increase  body  weight  it  is  neces- 
sary that  the  food  supply  be  in  excess  of  that  required  for  main- 
tenance and  for  the  production  of  heat  and  work.  When  such 
an  excess  is  given,  the  protein  and  ash  are  in  part  converted  into 
new  tissue,  and  the  fats,  carbohydrates  and  possibly  proteins, 
stored  up  in  the  form  of  fat.  Feeding  a  young  animal  an  excess 
will  promote  the  further  development  of  bone  and  muscle,  while 
in  the  case  of  the  mature  animal,  the  increase  will  come  almost 
wholly  from  the  deposition  of  fat  in  the  tissues.  In  both  in- 
stances fat  forms  the  largest  proportion  of  the  increase.  This  is 
shown  in  the  following  figures : — 

Composition  of  Increase  When  Steers  are  Fattening. 

Water        Ash         Protein       Fat 
Per  cent  Per  cent    Per  cent  Per  cent 

Oxen,  fattening  very  young 32-37        2.25  10  50-55 

Matured  animals,  final  period..  25-30        1.5  7-8        60-65 

These  figures  serve  to  illustrate  how  the  food  is  used,  and  that 
the  increase  is  largely  fat  formation.  A  satisfactory  gain  of  2 
pounds  per  day  would  then  mean  a  storage  of  1.3  to  1.5  pounds 
of  dry  substance,  of  which  about  0.2  pound  is  protein.  From  the 
fact  that  carbohydrates  can  serve  as  sources  of  fat,  it  is  evident 
that  the  non-protein  part  of  a  ration  may  be  the  chief  source  of 
the  increase  laid  on  by  a  fattening  animal.  The  protein  require- 


Food  Requirements  of  Animals.  259 

ment  for  the  constructive  work  is  apparently  small.  It  would 
appear  from  this  that  the  nutrients  serving  mainly  for  fat  forma- 
tion need  not  come  from  proteins  in  the  ration,  but  rather  from 
the  fats  and  carbohydrates.  Further,  from  a  theoretical  point  of 
view,  this  would  lead  us  to  the  conclusion,  that  for  fairly  mature 
fattening  animals  the  nutritive  ratio  may  be  wider  than  that 
recommended  in  the  German  standards.  These  standards  call 
for  a  ratio  of  from  1 :5  to  1 :7  in  the  various  classes  of  fattening 
farm  animals. 

Kellner,  from  experiments  on  oxen,  declares  that  a  fattening 
ration  may  vary  in  its  nutritive  ratio  from  1 :4  to  1 :10  without 
affecting  the  amount  of  increase  per  unit  of  digestible  matter, 
provided  the  nutrients  supplied  above  maintenance  come  from 
easily  digestible  feeding  stuffs.  Armsby,  in  his  standards  for 
fattening  steers,  provides  no  additional  protein  above  mainte- 
nance, only  allowing  additional  therms,  which  simply  represent 
material  for  fuel  and  fat  formation.  Certain  practical  feeding  ex- 
periments show  that  wide  rations  have  been  as  effective  as  the 
narrower  ones.  On  the  other  hand  there  are  experiments  of  this 
class  which  show  more  rapid  gains  when  a  larger  proportion  of 
protein  was  furnished.  Possibly  these  are  to  be  explained  on  the 
basis  of  increased  palatability  and  variety  of  nutrients,  thereby 
securing  an  increased  consumption.  The  proportion  of  protein 
was  probably  a  minor  factor.  When  the  nutrients  supplied  secure 
palatability,  ease  of  digestion  and  bowel  regulation,  it  is  probable 
that  they  need  not  be  of  very  highly  nitrogenous  character. 

Facts  bearing  on  this  point  are  disclosed  in  the  pig  feeding  ex- 
periments at  the  Rothamsted  Station  and  are  appended  in  the 
following  table. 

The  figures  in  the  last  column  are  not  the  nutritive  ratios, 
which  apply  to  digestible  matter,  but  simply  the  ratios  of  nitro- 
genous to  non-nitrogenous  matter.  The  true  nutritive  ratio  would 
be  considerably  wider.  The  results  clearly  show  that  100  pounds 
of  increase  were  produced  with  practically  the  same  consumption 


260 


Agricultural  Chemistry. 


of  organic  matter,  notwithstanding  the  great  variations  in  the 
quantity  of  protein  supplied. 

In  the  case  of  sheep,  the  fattening  process  is  not  greatly  unlike 
that  of  steers,  the  increase  being,  however,  somewhat  richer  in 
fat. 

It  is  probable  then,  that  for  fattening  animals  a  nutritive  ratio 
somewhat  under  that  recommended  by  the  Wolff  standards  is  not 
inconsistent  with  successful  feeding.  However,  if  the  animal  is 
still  growing,  then  it  is  apparent  that  a  wide  ratio  is  not  con- 

Fattening  Pigs  on  Food  Rich  and  Poor  in  Protein. 


Food  Supplied 

Consumed  to  produce  100  Ibs. 
of  gain 

Ratio  of 
protein  to 
non- 
protein 

Protein 
substance 

Non- 
protein 
substance 

Total 
organic 
matter 

Beans  and  lentil  meal  

Lbs. 
137 
113 

81 
80 

72 
72 
58 

Lbs. 
291 
297 
329 
340 
338 
366 
362 

Lbs. 
428 
410 
410 
420 
410 
438 
420 

1:2.1 
1:2.6 
1:4.1 
1:4.2 
1:4.7 
1:5.1 
1:6.3 

Beans,  lentil  and  corn  

Starch,  sugar,  lentil,  bran  
Starch,  lentil,  bran  

Corn,  bean   lentil,  bran   ...    . 

Corn,  bean  and  lentil  

Corn  and  bran  .       

ducive  to  best  results.  From  this  it  follows  that  the  home 
fodders  and  grains  can  furnish  the  main  sources  of  the  nutrients 
required  for  fattening  purposes.  It  must  always  be  kept  in  mind, 
however,  that  mere  mathematical  formulas  should  not  form  the 
basis  for  calculating  supplies  for  the  living  organism.  The  feeder 
recognizes  the  value  of  a  little  oil  meal  and  middlings  in  keeping 
the  animal  in  "condition"  for  best  results,  but  it  is  not  to  be 
assumed  that  their  entire  value  lies  in  their  protein  content.  The 
economy  of  a  ration  may  not  always  depend  upon  its  capacity  to 
form  an  increase.  It  may  be  decidedly  to  the  farmer's  advantage 
to  enrich  the  food  with  such  materials  as  bran  and  highly  nitro- 


Food  Requirements  of  Animals. 


261 


genous  foods  for  the  purpose  of  increasing  the  value  of  the  manure 
produced,  and  in  this  way  to  maintain  and  increase  the  fertility 
of  the  land. 

Before  leaving  this  subject  it  may  be  valuable  to  call  attention 
to  the  relative  efficiency  of  the  different  classes  of  farm  animals 
as  transformers  of  food  into  body  increase.  Warington  furnishes 
some  interesting  data  on  this  point : — 


Per  1000  Ibs.  live  weight 
per  week 

Required  to  produce 
100  pounds  increase 

Dry 
matter 
consumed 

Digested 
organic 
matter 

Increase 
in  live 

weight 

Dry  food 
consumed 

Digested 
organic 
matter 

Oxen 

Lbs. 
125 
160 
270 

Lbs. 
88 
121 
227 

Lbs. 
11.3 
17.6 
64.3 

Lbs. 
1,109 
912 
420 

Lbs. 

777 
686 
353 

Sheep 

Pies 

It  will  be  seen  that  in  proportion  to  its  weight,  the  sheep  eats 
more  food  and  yields  more  increase  than  the  ox,  while  the  pig 
consumes  more  food  and  returns  much  more  increase  than  either. 
This  is  due  to  the  concentrated  and  easily  digestible  character  of 
the  food  supplied  the  fattening  pig.  It  must  expend  compara- 
tively little  energy  in  preparing  the  material  for  assimilation. 
Again,  the  digestive  apparatus  of  ruminants  is  anatomically  dif- 
ferent from  that  of  the  pig.  In  the  former  the  capacity  for  the 
storage  of  rough  fodders  is  large,  but  the  proportion  of  intestine, 
where  absorption  is  most  active,  is  much  smaller  than  in  the  pig. 

Requirements  for  wool  production.  Wool  is  the  hair  of  sheep  : 
but  the  hair  of  certain  goats,  such  as  the  alpaca,  cashmere,  and 
mohair,  as  well  as  that  of  the  camel,  is  also  classed  as  wool.  Wool 
differs  from  ordinary  hair  only  in  its  physical  structure,  being 
covered  with  minute,  overlapping  scales,  and  having  a  twisted 
or  curled  fiber.  Wool  has  great  affinity  for  water  and  may  con- 
tain from  8  to  12  per  cent  of  moisture  in  hot,  dry  weather,  and  up 


262  Agricultural  Chemistry. 

to  50  per  cent  in  damp  weather.  Raw  wool  consists  of  (1)  yolk 
or  wool-grease;  (2)  suint;  and  (3)  the  pure  wool  hair.  The  first 
two  may  constitute  from  30  to  80  per  cent  of  the  weight  of  the 
unwashed  wool.  The  yolk  is  made  up  of  fatty  or  wax-like  bodies, 
of  complex  composition  and  insoluble  in  water.  In  a  washed 
fleece  the  yolk  may  vary  from  more  than  30  per  cent  to  less  than 
8  per  cent.  Short  fine  wool  contains  the  largest  proportion  of 
yolk.  The  suint  is  an  excretion  of  the  perspiration  glands  of  the 
skin  and  consists  of  potassium  salts  of  fatty  acids,  together  with 
phosphates,  sulphates  and  chlorides.  It  is  soluble  in  water  and 
consequently,  removed  by  washing.  It  may  amount  to  50  per  cent 
of  the  weight  of  unwashed  wool,  but  with  a  sheep  exposed  to  the 
weather,  the  quantity  may  be  15  per  cent  or  less. 

The  pure  wool  fiber  is,  for  the  most  part,  a  protein  and  contains 
about  16  per  cent  of  nitrogen  and  3.6  per  cent  of  sulphur.  A 
large  proportion  of  the  nitrogen  of  a  sheep  ?s  body  is  found  in  the 
wool.  The  fact  that  wool  production  is  at  the  expense  of  proteins 
must  indicate  that  a  somewhat  narrower  ration  is  demanded  than 
for  mere  fattening.  Wolff  fed  two  sheep  on  rations  consisting  of 
hay  and  bean  meal,  which  supplied  proteins  liberally  and  main- 
tained the  weights  of  the  animals.  Two  others  received  at  the 
same  time,  oat  straw  and  roots,  and  lost  slightly  in  weight.  The 
yield  of  pure  wool  fiber  in  the  first  case  was  12.9  pounds  and  in 
the  second  10.0  pounds.  It  appears  from  this  that  under  poor 
treatment  the  yield  of  wool  will  be  seriously  diminished.  Ex- 
periments further  show  that  on  liberal  fattening  rations,  the  pro- 
duction of  wool  is  no  greater  than  when  the  ration  is  just  sufficient 
to  maintain  the  animal.  However,  from  the  experiments  of  others. 
it  appears  that  on  somewhat  scanty  rations,  the  body  may  lose 
weight  without  the  production  of  wool  being  seriously  affected. 
All  this  emphasizes  the  fact  that  for  the  health  and  vigor  of  the 
animal  producing  this  nitrogenous  coat,  the  protein  supply  must 
not  fall  too  low. 

The  high  favor  in  which  such  root  crops  as  turnips  and  ruta- 
bagas are  held  by  sheep  feeders  may  find  its  explanation  in  their 


Food  Requirements  of  Animals.  263 

richness  in  sulphur,  which  we  have  seen  constitutes  a  considerable 
proportion  of  the  pure  wool  fiber. 

Requirements  for  milk  production.  Milk  ultimately  comes 
from  the  food  and  its  direct  purpose  is  for  the  nutrition  of  the 
young.  For  this  reason  its  production,  so  far  as  possible,  is  made 
independent  of  the  immediate  food  supply.  If  the  surplus  food 
given  a  fattening  ox  is  withdrawn  to  a  maintenance  requirement, 
the  laying  on  of  increase  will  immediately  cease ;  but  the  food  of 
a  milking  cow  may  be  reduced  to  maintenance,  without  stopping 
the  production  of  milk.  The  animal  will  continue  to  produce 
milk,  drawing  for  its  source  from  her  own  body.  The  quantity 
produced  will  decrease  and  the  animal  will  steadily  grow  thinner. 
A  minimum  food  supply  will  not  entirely  stop  milk  production, 
neither  will  an  over-abundant  supply  raise  the  milk  production 
beyond  certain  limits.  Each  cow  has  an  inherent  milk  producing 
capacity,  determined  by  breed  and  individuality.  Above  this  it 
is  rarely  possible  to  go,  but  whether  this  capacity  is  reached  will 
depend  upon  food  and  treatment.  Excess  of  food  will  simply 
tend  to  fatten.  Generous  feeding  will  not  make  a  good  milch  cow 
out  of  a  poor  one,  but  it  will  sustain  a  full  flow  of  milk  and  extend 
the  period  of  profitable  production. 

There  is  only  one  way  to  determine  whether  a  cow  is  profitable, 
and  that  is  by  determining  her  yield  of  milk  and  the  amount  of 
marketable  constituents  it  contains.  To-day,  this  is  entirely  done 
on  the  basis  of  the  quantity  of  fat  the  milk  contains,  which  gives 
the  animal's  capacity  for  butter  production.  To  measure  the 
capacity  of  her  milk  for  cheese  production,  both  fat  and  casein 
must  be  determined.  From  the  standpoint  of  economy  in  trans- 
forming  feed  stuffs  into  human  food,  the  total  milk  solids,  and 
not  the  milk  volume,  should  be  the  basis  for  estimation. 

The  quantity  of  nutrients  necessary  to  make  100  pounds  of 
Jersey  milk,  other  things  being  equal,  is  greater  than  that  re- 
quired to  produce  the  same  weight  of  Holstein  milk.  From  the 
standpoint  of  the  farmer  the  most  profitable  cow  is  the  one  pro- 


264  Agricultural  Chemistry. 

ducing  the  largest  return  in  butter  fat,  butter  fat  and  casein,  or 
total  milk  solids  per  unit  of  food  consumed. 

The  transformation  of  digestible  feed  material  into  human  food 
by  the  dairy  cow  far  exceeds  that  produced  in  the  same  time  by 
the  growing  or  fattening  ox  and  slightly  exceeds  that  produced  in 
swine.  An  ox,  gaining  2  pounds  per  day,  will  yield  in  edible 
solids  about  1.5  pounds,  while  a  dairy  cow,  producing  30  pounds 
of  milk  containing  12  per  cent  of  solids,  will  yield  3.6  pounds. 
Based  on  pounds  of  digestible  nutrients  consumed,  Jordan  has 
given  us  some  interesting  figures.  They  are  general  averages 
and  are  given  in  the  following  table ;  they  represent  the  pounds 
of  edible  solids  produced  by  100  Ibs.  of  digestible  organic  matter 
in  the  ration. 

Relation  of  Food  to  Produce. 

Edible  solids 

Lbs. 

Milk 18.0 

Steers,  (carcass) 2.52 

Lambs 2 . 60 

Swine 15 . 60 

Calves 8.10 

Fowl 4.20 

Eggs 5.10 

The  quantity  of  solids  in  the  cow 's  milk,  per  unit  of  feed  con- 
sumed, thus  always  exceeds  the  quantity  of  solids  produced  in 
the  increase  of  the  fattening  ox,  and  in  the  order  of  food  effi- 
ciency the  cow  leads  the  list. 

Milk  is  a  highly  nitrogenous  substance,  and  its  proteins  must 
be  made  from,  protein.  They  can  have  no  other  ultimate  source 
but  the  feed  and  cannot  be  produced  from  fats  or  carbohydrates. 
Thirty  pounds  of  average  milk  will  contain  a  pound  of  protein. 
This  daily  drain  means  that  the  ration  of  the  dairy  cow  must 
be  reasonably  narrow.  If  0.6  pound  of  protein  is  needed  for 
maintenance,  then  1.6  pounds  must  be  used  daily.  Practice  and 
science  have  established  the  quantity  of  digestible  organic  matter 


Food  Requirements  of  Animals.  265 

necessary  for  economical  milk  production  at  from  15.5  to  16.5 
pounds  per  day  for  a  good  cow  of  average  size.  The  quantity  re- 
quired may  va,ry  somewhat  according  to  size, — a  small  cow  re- 
quiring proportionately  somewhat  more  than  a  larger  one  for  the 
same  yield  of  milk, — but  capacity  for  production  is  the  more  im- 
portant factor  in  determining  the  quantity  of  feed  required. 
With  that  amount  of  digestible  nutrients,  the  nutritive  ratio 
would  be  about  1 :9.5.  Careful  experiments,  however,  show  that 
a  nutritive  ratio  of  1 :5.5  to  1 :6.5  is  more  efficient  than  the  wider 
one,  and  that  a  cow  of  average  size  and  good  capacity  should  re- 
ceive at  least  2.25  pounds  of  digestible  protein  daily,  with  a  nu- 
tritive ratio  not  wider  than  1 :6.5.  Young  pasture  grass,  well 
known  to  be  an  efficient  milk  producer,  is  even  narrower  than  this. 
The  function  of  this  additional  protein  is  not  known,  but  the  ac- 
cepted axiom  that  proteins  stimulate  the  metabolic  activities  of 
the  cells  is  borne  out  here,  with  an  intensified  milk  secretion  as 
the  result.  On  the  other  hand,  excessive  protein  feeding  may 
be  injurious  and  certainly  is  not  necessary. 

It  has  been  taught  that  the  fats  of  milk  originate  from  the 
protein  and  food  fats.  If  true,  this  would  increase  the  demand 
for  protein,  but  experiments  have  clearly  demonstrated  that  they 
are  not  a  necessary  source  of  milk  fat.  In  a  carefully  conducted 
experiment  at  the  New  York  Experiment  Station,  Jordan  con- 
clusively showed  that  the  carbohydrates  of  the  food  could  serve 
as  milk-fat  formers. 

The  food  consumed  by  the  dairy  cow  during  the  first  half  of 
the  lactation  period  is  largely  used  in  milk  production,  but  during 
the  latter  portion  of  lactation  it  is  partly  consumed  in  building 
the  calf,  and  the  return  in  milk  is  reduced.  A  newly-born  calf 
weighing  80  pounds,  may  contain  20  pounds  of  protein,  3  pounds 
of  fat,  and  the  rest  will  be  water  and  ash. 

From  what  has  been  said  on  the  necessity  of  a  proper  protein 
supply  for  the  milch  cow,  it  is  apparent  that  where  the  home 
grown  crops  are  the  hays  made  from  true  grasses  and  where  the 
corn  crop  is  the  chief  one  raised,  then  home-grown  rations  for 


266  Agricultural  Chemistry. 

maximum  efficiency  in  milk  production  are  not  possible.  Where, 
however,  alfalfa  and  clover  make  the  hay,  and  peas  and  oats  are 
•rrown,  a  protein  supply  consistent  with  efficiency  can  be  pro- 
duced. 

There  is  the  additional  fact  that  the  production  of  milk  de- 
mands a  plentiful  ash  supply  to  the  animal.  Thirty  pounds  of 
milk  will  contain  nearly  an  ounce  of  lime  and  the  same  quantity 
of  phosphoric  acid.  Besides  the  quantities  secreted  in  the  milk, 
there  is  apparently  a  waste  from  cell  activity,  which  in  the  case 
of  a  dairy  cow  yielding  30  pounds  of  milk,  was  found  to  be  nearly 
equal  to  the  quantity  secreted  in  the  milk.  In  an  experiment  at 
the  Wisconsin  Station,  where  a  ration  was  made  up  of  oat  straw, 
rice,  wheat  bran  and  wheat  gluten,  a  cow  continued  to  give  a  milk 
of  constant  composition  in  respect  to  lime  content,  as  well  as  all 
other  constituents;  yet  the  amount  of  lime  supplied  the  animal, 
for  a  period  of  over  100  days,  had  been  deficient.  To  maintain  a 
normal  composition  of  the  milk,  the  animal  had  withdrawn  lime 
from  her  skeleton,  a  remarkable  transmigration  of  material.  The 
health  of  the  animal  was  apparently  unimpaired,  but  it  is  self- 
evident  that  ultimately  the  milk  flow  must  have  ceased  or  the 
animal  would  have  collapsed.  While  the  ration  used  was  unusual, 
the  experiment,  however,  emphasizes  the  necessity  of  a  liberal 
supply  of  ash  material  for  the  dairy  cow.  The  legume  seeds  and 
cereal  grains  are  low  in  lime,  but  are  fairly  rich  in  phosphorus. 
Wheat  bran  is  relatively  poor  in  lime,  but  rich  in  phosphorus. 
Ten  pounds  of  bran  will  supply  about  one-fourth  of  an  ounce  of 
lime,  but  nearly  one-third  of  a  pound  of  phosphoric  acid.  The 
hays  from  the  true  grasses  are  fairly  wejl  supplied  with  lime, 
but  the  legume  hays,  as  clover  and  alfalfa,  are  particularly  rich 
in  this  material,  and  should,  for  this  reason,  form  a  part  of  the 
nit  ion  of  the  dairy  cow. 

It  would  appear,  then,  that  in  most  rations  recognized  by 
dairymen  as  efficient  for  milk  production,  phosphoric  acid  and 
lime  will  be  plentifully  supplied,  especially  where  bran  and  the 
legume  hays  constitute  a  part  of  the  ration.  But  should  straws 
form  the  niuLrlui'jr.  th<>  supply  of  lime  may  become  deficient. 


CHAPTER  XII 

MILK  AND  ITS  PRODUCTS. 

Milk  is  a  valuable  agricultural  product  and  both  it  and  the 
products  obtained  from  it  are  of  considerable  commercial  and  in- 
dustrial importance.  The  dairy  products  of  the  State  of  Wis- 
consin alone  are  valued  at  $75,000,000. 

Secretion.  Milk  is  the  secretion  of  special  glands  in  the  mam- 
malian female  and  adapted  to  the  nourishment  of  the  newly  born 
young  of  that  particular  species.  The  constituents  of  the  milk 
are  especially  elaborated  by  the  cells  of  the  mamma;  these  con- 
stituents do  not  exist  preformed  in  the  blood,  but  are  formed  by 
profound  chemical  processes,  little  understood,  out  of  the  nu- 
trients carried  in  the  blood  to  the  active  cells.  For  example,  no 
casein  or  milk  sugar  exists  either  in  the  food  of  the  cow  or  in  her 
blood,  but  from  the  nitrogenous  constituents  of  blood,  the  com- 
plex protein,  casein,  is  elaborated ;  also,  from  the  simple  sugar 
dextrose,  the  more  complex  milk  sugar  is  formed.  This  is  all 
accomplished  through  the  wonderful  activities  of  the  udder  cells. 
That  the  composition  of  the  milk  is  closely  related  to  the  food  re- 
quirements of  the  newly  born  young  and  its  rate  of  growth,  has 
been  suggested  by  the  physiologist,  Bunge.  This  relates  partic- 
ularly to  the  ash  and  protein  materials  of  milk,  which  are  so 
necessary  for  the  life  processes  and  the  rapid  building  of  the 
growing  young. 

The  following  table  will  clearly  show  that  the  ash  of  milk  and 
of  the  new  born  young  are  very  much  alike,  while  they  have  an 
entirely  different  composition  from  the  fluid  out  of  which  they 
are  formed,  namely  the  blood,  and  especially  the  blood  serum; 
from  a  consideration  of  such  facts,  it  appears  certain  that  the 
cells  of  the  milk  gland  must  possess  the  power  of  selection  and 
that  milk  is  not  merely  filtered  from  the  blood. 


268 


A gr  icultural  Chemistry. 


Comparative  Composition  of  the  Milk,  Blood  and  Body 
of  the  Same  Animal. 


100  Parts  by  weight  of  ash  contained  in  grams 


Dog  a  few 
hours  old 

Dog's  milk 

Dog's  blood 

Dog's  blood 
serum 

Potash 

11  14 

15  0 

3.1 

2.4 

Soda  

10.6 

8.8 

45.6 

52.1 

Lime  

29.5 

27.2 

0.9 

2.1 

Magnesia 

1  8 

1.5 

0.4 

0.5 

Phosphoric  acid  

39.4 

34.2 

13.3 

5.9 

If  we  compare  the  time  required  by  the  suckling  to  double 
its  weight  at  birth,  with  the  amounts  of  protein  and  ash — per- 
haps the  most  essential  constituents  for  the  formation  of  tissue — 
contained  in  100  parts  of  milk,  it  is  evident  at  a  glance  that  the 
amounts  of  these  increase  in  proportion  to  the  rate  of  growth  of 
the  animal.  This  is  shown  in  the  following  table: — 

Composition  of  Milk  Ash  from  Different  Animals. 


Species 

Days 
required 
to  double 
weight 

100  parts  by  weight  of  milk 
contains  in  grams 

Protein 

Ash 

Lime 

Phos- 
phoric 
acid 

Man  

180 
60 
47 
22 
15 
14 

p 

6 

1.6 
2.0 
3.5 
3.7 
4.9 
5.2 
7.0 
7.4 
14.4 

0.2 
0.4 
0.7 
0.78 
0.84 
0.80 
1.02 
1.33 
2.50 

0.03 
0.12 
0.16 
0.20 
0.25 
0.25 

0.05 
0.13 
0.20 

0.28 
0.29 
0.31 

Horse  

Cow  

Goat 

Sheep 

PiK  , 

Cat  

Dog  .  .  . 

0.45 
0.89 

0.51 
0.99 

Rabbit  ...   . 

Milk  and  Its  Products.  269 

The  composition  of  the  milk  of  a  single  species  is  by  no  means- 
similar  to  that  of  another,  although  the  constituents  forming  it, 
so  far  as  they  have  been  investigated,  are  of  a  similar  nature. 

The  constituents  of  milk  may  be  divided  into  the  following 
classes:  water,  fats,  proteins,  sugar  and  ash.  The  water  of 
milk  constitutes  from  85  to  88  per  cent  and  needs  no  discussion. 

Fats  of  milk.  The  fats  resemble  in  chemical  constitution  the 
animal  and  vegetable  oils  and  fats  already  discussed;  that  is, 


The  milk  chambers  or  alveoli  of  an  udder;  A  and  B,  secreting  alveoli; 
C  and  D,  non-secreting  alveoli;  E,  alveolus,  which  has  discharged 
its  milk  (cells  appear  flattened). 

they  consist  of  compounds  of  fatty  acids  and  glycerine.  They 
differ  from  animal  fats  chiefly  in  containing  acid  radicals  of  low 
molecular  weight,  in  addition  to  the  heavy  acids,  such  as  oleic, 
stearic,  and  palmitic,  which  are  the  principal  fatty  acids  in  the 
fats  of  animal  tissue.  Butter  fat  consists  of  the  glycerides  of 
at  least  9  fatty  acids.  The  lowest  member  of  the  group  is  butyric 
acid,  the  highest  is  stearic  acid.  Oleic  acid  belongs  to  another 


Agricultural  Chemistry. 


series.     The  average  percentage  composition  of  milk  fat  is  about 
as  follows: — 


Per  cent 

Butyrin 3.85 

Caproin 3.60 

Caprylin 0.55 

Caprin 1.90 

Laurin  . .  7.40 


Per  cent 

Myristin  20.20 

Palmitin 25.70 

Stearin 1.80 

Olein..  35.0 


The  properties  of  these  fats  are  variable,  but  the  important 
fact  to  notice  is  the  occurrence  in  milk  fat  of  the  first  three  or 
four  fats  in  the  above  list,  but  mere  traces  of  which  are  present 
in  other  animal  fats.  Olein  and  the  first  four  members  of  the 
above  list  are  liquid  fats ;  the  others  are  solid,  stearin  being  the 
hardest.  About  8.0  per  cent  of  the  fatty  acids,  chiefly  consisting 
of  the  first  three  in  the  series,  are  soluble  in  water.  The  soluble 
acids  have  a  low  boiling  point  and  can  be  separated  from  the  other 
fatty  acids  by  distillation.  These  facts  serve  to  distinguish  butter 
fat  from  animal  fats  such  as  tallow,  which  contains  but  traces  of 
soluble  and  volatile  fatty  acids.  Milk  fat,  however,  varies  con- 
siderably both  in  composition  and  physical  properties,  being 
affected  somewhat  by  feed,  period  of  lactation  and  other  circum- 
stances under  which  the  cows  are  kept. 

Fat  exists  in  milk  in  the  form  of  minute  globules,  varying  in 
diameter  from  .0016  to  .010  m.  m.  In  the  milk  of  Jersey  and 
Guernsey  cows  the  average  size  of  the  globules  is  considerably 
larger  than  in  Holstein  milk ;  also  in  the  milk  of  recently  calved 
cows  the  globules  are  larger  than  in  that  of  cows  far  advanced  in 
lactation.  This  fact  has  an  important  practical  bearing  upon 
the  speed  with  which  cream  rises.  The  milk  of  the  Jerseys  and 
Guernseys  throws  up  its  cream  very  rapidly,  while  from  the  milk 
of  the  Holstein  and  Ayrshire  breeds  the  cream  rises  relatively 
slower. 

The  proteins.  The  two  most  important  proteins  of  milk  are 
casein  and  albumin.  Traces  of  others  are  present,  but  they  are 


Milk  and  Its  Products.  27  I 

in  such  relatively  small  quantities  that  they  will  not  be  dis- 
cussed here. 

Casein  is  the  chief  protein  of  milk  and  exists  there  in  a  col- 
loidal state  and  not  in  perfect  solution.  It  can  be  separated  from 
the  milk  by  the  addition  of  an  acid  or  by  the  action  of  the  enzyme, 
rennin,  which  is  contained  in  rennet.  In  the  souring  of  milk, 
during  which  process  acid  is  developed,  the  casein  is  precipitated. 
The  casein  formed  in  this  way  probably  consists  of  calcium-free 
casein,  for  it  is  generally  held  that  casein  exists  in  milk  in  com- 
bination with  calcium.  AVith  rennin,  however,  the  calcium-casein 
is  split  into  two  compounds,  para-casein  and  whey  protein.  The 
para-casein  in  the  presence  of  the  soluble  calcium  salts  of  the 
milk  precipitates  out,  while  the  whey  protein  remains  in  solution. 
In  the  absence  of  calcium  salts  rennin  will  not  curdle  milk.  This 
enzyme  acts  best  at  35°  C.  and  is  destroyed  at  70°  C.  It  is  found 
in  the  stomachs  of  all  mammals,  while  enzymes  possessing  similar 
properties  have  also  been  found  in  birds,  fishes,  many  plants,  and 
in  the  products  formed  by  the  action  of  certain  bacteria. 

Mere  boiling  of  milk,  unless  continued  for  a  considerable  time, 
does  not  coagulate  the  casein.  Casein  is  the  only  protein  of 
cow's  milk  which  contains  phosphorus  in  its  molecule. 

Milk  albumin  differs  in  some  of  its  physical  properties  from 
blood  albumin.  It  is  in  complete  solution  in  milk  but  coagulates 
and  precipitates  when  heated  to  72°  C.  It  is  not  coagulated  by 
rennin  or  by  most  acids.  It  differs  from  casein  in  composition 
and  contains  about  twice  as  much  sulphur  and  no  phosphorus. 
In  colostrum  milk,  albumin  largely  predominates,  so  that  the 
milk  coagulates  on  heating. 

Milk  sugar.  The  sugar  contained  in  milk  is  known  as  lactose. 
It  occurs  in  the  milk  of  all  animals,  but  is  not  present  in  plants, 
and  consequently  does  not  exist  in  the  food  of  the  dairy  cow. 
It  is  prepared  by  evaporating  the  whey,  left  after  cheese  making, 
to  a  small  bulk,  from  which  lactose  will  crystallize  out  in  large 
crystals.  It  possesses  a  faint  sweet  taste,  about  one-tenth  that 


27:.'  Agricultural  Chemistry. 

of  cane  sugar.     By  the  action  of  dilute  acids  or  an  enzyme  known 
as  lactase,  it  is  split  into  a  mixture  of  dextrose  and  galactose. 

Milk  sugar  does  not  readily  undergo  alcoholic  fermentation. 
but  is  readily  changed  into  lactic  acid  by  certain  micro-organ- 
isms. This  change  in  the  milk  sugar  is  the  cause  of  milk  souring. 
The  necessary  lactic  organisms  are  very  abundant  everywhere, 
especially  in  the  vicinity  of  dairies  and  barns,  and  as  they 
multiply  in  the  milk,  more  and  more  lactic  acid  is  formed.  Sweet 
milk  has  an  acidity  of  from  0.12  to  0.20  per  cent,  expressed  as 
lactic  acid.  When  about  0.40  per  cent  is  present,  the  milk  ac- 
quires a  sour  taste,  and  when  the  amount  reaches  0.6  to  0.7  per 
cent,  curdling  commences.  "With  certain  organisms,  the  amount 
of  lactic  acid  may  reach  from  2.0  to  3.0  per  cent,  but  ordinarily 
it  does  not  exceed  0.9  per  cent. 

The  ash  of  milk.  "When  water  is  removed  from  milk  by  evap- 
oration and  the  residue  then  burned,  a  white  ash  is  always  left 
behind.  This  consists  of  the  mineral  matter  and  salts  of  the 
milk,  together  with  sulphates,  phosphates  and  carbonates  pro- 
duced by  the  burning  of  the  organic  matter  of  the  milk.  It 
amounts  in  cow's  milk  to  about  0.7  per  cent,  and  consists  of: — 


Per  cent 

Potash m....  22      to  27 

Soda "....   10      to  12 

Lime 19      to  24 

Magnesia 1.8  to    3 


Pei'  cent 

Ferric  oxide traces  to    0.2 

Sulphur  trioxide 3.8to    4.4 

Phosphoric  acid 22      to  27 

Chlorine..  ....    13      to  16 


Milk  also  contains  traces  of  citric  acid.  This  is  not  free,  but 
in  combination  with  bases  as  citrates  and  amounts  to  about  0.1 
per  cent  of  the  milk. 

The  gases  of  fresh  milk  are  chiefly  carbon  dioxide,  oxygen  and 
nitrogen.  These  amount  to  about  85  c.  c.  per  liter,  the  carbon 
dioxide  constituting  approximately  90  per  cent  of  the  total  gas. 
On  standing,  or  even  during  the  process  of  milking,  there  is  a 
rapid  exchange  of  gases,  the  carbon  dioxide  greatly  diminishing, 
while  tin-  oxygen  and  nitrogen  rapidly  increase.  This  increase 


Milk  and  Us  Products.  273 

in  oxygen  and  nitrogen  is  really  an  absorption  of  air  and  em- 
phasizes the  necessity  of  maintaining  a  pure,  sweet  atmosphere, 
to  which  fresh  milk  is  to  be  exposed. 

Physical  properties.  Milk  is  a  white,  or  yellowish  white, 
opaque  fluid,  with  a  sweet  taste.  The  specific  gravity  varies 
usually  from  1.027  to  1.034.  The  solids  other  than  fat  tend  to 
raise  the  specific  gravity,  while  the  fat  tends  to  lower  it.  As 
cream  may  be  removed  and  water  added  without  altering  the 
specific  gravity,  no  safe  conclusion  as  to  the  quality  of  the  milk 
can  be  based  on  this  test  alone.  When  fresh  milk  is  quickly 
cooled  and  its  specific  gravity  taken  at  once,  and  then  again  after 
some  hours  and  at  the  same  temperature,  a  small  but  decided 
rise  in  density  is  observable,  usually  amounting  to  about  0.0005. 
This  is  known  as  Kechnagel's  phenomenon,  and  has  been  ex- 
plained in  several  ways.  It  has  been  ascribed  to  the  escape  of 
gases  from  the  milk ;  to  a  change  in  the  mechanical  condition  of 
the  casein;  and  lastly  to  the  solidification  of  the  fat  globules. 
It  is  suggested  that  quick  cooling  does  not  immediately  solidify 
the  fat  globules,  which  are  liquid  at  the  temperature  of  the  cow, 
but  that  they  remain  in  a  super-cooled  liquid  state.  As  they 
slowly  solidify,  they  contract,  thereby  increasing  the  density  and 
raising  the  specific  gravity. 

Chemical  composition.  This  varies  considerably  according 
to  breed,  individuality,  age,  period  of  lactation  and  food.  The 
mean  composition,  according  to  many  American  analyses,  is 
as  follows: — 


Per  cent 

Water 87.1 

Fat  3.9 

Sugar 5.1 


Per  cent 

Casein 2.5 

Albumin 0.7 

Ash..  0.7 


It  must  be  remembered  that  these  figures,  being  averages,  im- 
ply the  existence  of  many  values  either  above  or  below  those 
given.  As  a  rule  the  fat  is  most  liable  to  variation.  The  fac- 
tors influencing  the  composition  of  milk  will  be  briefly  discussed 
under  the  following  heads: — 


274 


Agricultural  Chemistry. 


Breed.  It  is  well  known  that  breed  is  a  very  important  factor 
in  influencing  the  composition  of  milk.  The  following  table 
gives  the  average  composition  of  the  milk  from  several  individ- 
uals of  the  breed  represented.  Individual  variations  from  the 
figures  given  are  of  course  to  be  found,  and  the  figures  only 
represent  the  general  trend  of  the  breed. 

Composition  of  Milk  of  Different  Breeds. 


Name  of  breed 

Solids 

Fat 

Casein 

Albumin 

Holstein 

Per  cent 
11  80 

Per  cent 
3  26 

Per  cent 
2  20 

Per  cent 
64 

Ayrshire 

12.75 

3  76 

2  46 

61 

Shorthorn 

14  30 

4.28 

2  79 

64 

14  50 

4  89 

3  10 

83 

Guernsey 

14  90 

5  38 

2.91 

65 

Jersey 

15  40 

5  78 

3  03 

.65 

Individuality.  It  is  uncommon  to  find  in  a  herd  of  cowrs  of 
the  same  breed  any  two  individuals  whose  milk  is  of  the  same 
composition.  This  is  true  whether  we  consider  single  milkings 
or  the  average  of  many. 

Age.  So  far  as  there  are  published  data  on  the  influence  of 
the  age  of  cows  on  the  composition  of  milk,  they  indicate  a  ten- 
dency for  the  heifer  to  show  a  slightly  higher  fat  content  than 
the  mature  cow.  Individual  exceptions,  however,  are  not  in- 
frequent, and  more  data  are  needed  to  settle  the  question. 

Period  of  lactation.  Immediately  after  calving,  the  first  pro- 
duct of  the  udder  is  colostrum.  This  is  a  yellow  liquid,  of  strong, 
pungent  taste,  and  very  different  from  normal  milk.  It  is 
characterized  by  containing  small  clusters  of  cells,  known  as 
"colostrum  granules"  and  is  very  rich  in  albumin.  This  may 
reach  13.5  per  cent.  Because  of  the  high  content  of  albumin, 
colostrum  milk  sets  to  a  solid  mass  on  heating.  This  test  serves 
to  distinguish  it  from  normal  milk.  This  first  milk  is  exceed- 
ingly important  to  the  young  animal  at  birth,  and  serves  to 


Milk  and  Its  Products. 


275 


cleanse  the  alimentary  tract  and  properly  start  the  work  of  di- 
gestion. After  eight  or  ten  days  from  calving  the  secretion  be- 
comes like  normal  milk,  but  the  colostrum  cells  can  usually  be 
found  in  the  milk  for  about  14  days  after  calving. 

The  milk  during  the  first  month  after  calving  is  generally  rich 
in  fat  and  total  solids,  and  these  diminish  during  the  second 
month.  After  the  second  or  third  month,  the  fat  and  protein, 
as  well  as  the  sugar,  continue  to  increase  from  month  to  month 
during  the  entire  period  of  lactation.  The  following  table,  taken 
from  the  data  of  the  New  York  State  Station,  represents  the 
monthly  averages  of  nearly  100  different  lactation  periods. 

Influence  of  Lactation  on  th?  Composition  of  Milk. 


Month  of  lactation 

Fat 

Proteins 

Casein 

Albumin 

1  

Per  cent 
4  30 

Per  cent 
3.16 

Per  cent 
2.54 

Per  cent 
0  62 

•> 

4  11 

2  99 

2  42 

0  57 

3  

4.21 

3.04 

2  46 

0.58 

4  

4.25 

3.13 

2.52 

0.61 

5         

4.38 

3.25 

2.61 

0.64 

6.       .                   

4.53 

3  36 

2.68  ' 

0.65 

7         

4  57 

3.40 

2.74 

0.66 

<S                 

4.59 

3.47 

2.80 

0.67 

9. 

4  67 

3  57 

2.90 

0  67 

10 

4.90 

3.79 

3.01 

0.78 

11 

5  07 

4  04 

3  13 

0  91 

Occasionally  individuals  may  depart  from  the  general  ten- 
dency shown  in  the  above  table,  but  usually  they  conform  to  the 
general  rule  which  the  table  indicates.  The  average  size  of  the 
fat  globules  diminishes  with  advancing  lactation,  but  their  num- 
ber per  unit  volume  increases. 

Feed.  The  influence  of  the  feed  of  cows  upon  the  composition 
of  their  milk  is  a  matter  upon  which  many  varied  opinions  are 
held.  There  is  a  widespread  belief  that  this  influence  is  con- 
siderable, but  all  experimental  evidence  shows  it  to  be  very  small. 
Under  scanty  food  supply  the  quality  and  especially  the  quantity 


276  Agricultural  Chemistry. 

of  milk  may  be  considerably  reduced.  This  is  evidenced  by  the 
results  secured  at  the  Cornell  Station  with  a  poorly  fed  herd  and 
again  when  the  same  herd  was  liberally  fed.  Under  those  con- 
ditions, where  a  liberal  supply  of  nutrients  was  given,  the  flow 
of  milk  was  nearly  doubled  and  the  percentage  of  fat  slightly 
increased.  Again,  there  appears  to  be  some  distinct  evidence 
that  a  change  from  a  ration  with  a  wide  nutritive  ratio  to  one 
with  a  narrow  ratio,  is  for  a  time,  attended  with  a  production 
of  milk  slightly  richer  in  fat ;  but  the  change  is  only  transient, 
and  even  if  the  food  with  a  high  protein  ration  be  continued,  the 
milk,  after  allowance  is  made  for  the  effect  of  advancing  lacta- 
tion, shows  a  tendency  to  return  to  its  previous  composition. 

In  any  case,  it  appears  that,  provided  cows  are  sufficiently  fed, 
change  of  feed  has  very  little  permanent  effect  upon  the  com- 
position of  their  milk.  Violent  and  sudden  changes  in  the  char- 
acter of  their  feed  may  cause  a  sudden  fluctuation  in  the  com- 
position of  the  milk,  but  after  a  short  period  it  will  tend  to  re- 
turn to  a  composition  characteristic  for  that  animal. 

The  opinion  that  it  is  possible  to  feed  fat  into  milk  has  widely 
prevailed,  but  such  a  notion  is  based  upon  a  misconception  o 
how  milk  is  formed.  When,  however,  we  remember  that  the 
cells  of  the  mammary  gland  are  selective  in  function,  and  that 
with  the  same  feeds  a  Jersey  cow  always  makes  Jersey  milk,  and 
a  Holstein  cow  Holstein  milk,  then  the  many  failures  to  feed  fat 
into  milk  become  intelligible.  The  careful  and  well  planned 
work  of  Lindsey,  in  which  a  number  of  vegetable  oils  have  been 
added  to  a  basal  ration,  gave  in  some  cases  slight  but  only  tem- 
porary increases  of  fat  in  the  milk,  while  with  other  oils  no 
increase  whatever  was  noticed. 

Certain  feeds,  however,  affect  the  character  of  the  fat  in  the 
milk,  which  is  manifested  by  a  change  in  the  hardness  and  phys- 
ical properties  of  the  butter  produced.     It  is  agreed  that  cotton 
seed  meal  has  the  effect  of  raising  the  melting  point  of  butter 
while  gluten  feed,  rich  in  oil,  produces  a  softer  butter  of  lowe 
melting  point.     In  experiments  at  the  Wisconsin  Station,  Ion 


i 


Milk  and  Its  Products.  277 

continued  feeding  of  nutrients  entirely  from  the  corn  plant,  as 
well  as  from  the  wheat  plant,  tended  to  produce  soft,  low-melting 
milk  fats,  while  the  nutrients  from  the  oat  plant  produced  fats 
making  a  hard  butter,  with  a  high  melting  point. 

Season.  The  influence  of  season  upon  the  composition  of  milk, 
apart  from  the  effect  of  advancing  lactation,  is  largely  associated 
with  the  food  supply.  When  this  is  normally  maintained  and 
the  animals  are  protected  from  the  effect  of  weather  changes, 
variations  in  the  composition  of  the  milk  appear  to  be  slight. 

Time  and  intervals  between  milking.  Where  the  time  be- 
tween milkings  is  the  same  and  there  are  no  other  disturbing  in- 
fluences, the  composition  of  morning's  and  evening's  milk  shows 
practically  no  difference.  Where  the  intervals  are  unequal, 
there  may  be  a  considerable  variation  in  the  two  milkings.  In 
an  experiment  where  17  Shorthorn  cows  were  milked  at  6  a.  m. 
and  3  p.  m.  the  average  per  cent  of  fat  in  the  morning's  milk  was 
3.2,  and  4.5  per  cent  in  the  evening's  milk. 

It  is  well  known  that  the  first  milk  drawn  from  the  udder  at 
milking  time  is  very  low  in  fat,  sometimes  being  as  low  as  1  per 
cent,  while  the  last  portion  may  contain  as  high  as  10  per  cent. 
In  these  two  fractions,  however,  the  other  constituents  are  in 
about  the  same  proportion  as  would  be  found  in  the  entire  milk- 
ing. 

Milk  of  other  animals.  The  following  table  compiled  from 
several  sources,  gives  the  average  composition  of  the  milk  of 
other  animals;  some  of  the  results  are  probably  not  truly  rep- 
resentative, due  to  improper  sampling. 

There  is  a  considerable  difference  in  the  behavior  of  the  casein 
of  the  milk  of  different  animals  when  treated  with  rennet.  With 
cow's  milk  the  enzyme  of  rennet,  rennin,  gives  a  coherent,  curdy 
precipitate,  while  with  human  milk  the  coagulum  is  much  more 
finely  divided.  To  this  fact  has  been  attributed,  in  part,  the 
non-adaptability  of  cow's  milk  to  infant  feeding.  It  will  also 
be  noticed  that  cow's  milk  differs  from  the  natural  food  of  the 
human  infant  in  containing  more  ash  and  proteins  and  much  less 


278 


Agricultural  Chemistry. 


sugar.  It  is  upon  these  chemical  facts  that  the  modification  of 
cow 's  milk,  by  dilution  and  addition  of  lactose,  rendering  it  suit- 
able for  infant  feeding,  is  based.  However,  experience  is  teach- 
ing that  in  most  cases  the  whole  milk  of  the  cow,  without  dilution, 
'can  be  safely  used  for  infant  feeding.  There  is  a  growing  be- 
lief, though,  that  it  must  not  be  too  rich  in  fat. 

Preservation  of  milk.     Normal  milk  as  it  occurs  in  the  cow's 
udder  usually  contains  relatively   few  organisms;   but  in   the 

Composition  of  Milks. 


Animal 

Fat 

Casein 

Sugar 

Ash 

Solids 
not  fat 

Woman                    

Per  cent 
3.3 
1.0 
6.5 
5.3 
1.7 
4.6 
2.9 
4.5 
9.6 
3.3 
10.5 
19.6 
48.5 
43.7 

Per  cent 
1.5 
1.1 
4.3 
7.1 
2.2 
7.2 
3.8 
Trace 
9.9 
9.5 
15.5 
3.1 
11.2 
7.1 

Per  cent 
6.8 
5.5 
5.0 
4.2 
6.0 
3.1 
5.7 
4.4 
3.2 
4.9 
2.0 
8.8 
1.8 

Per  cent 
0.2 
0.4 
0.7 
0.8 
0.4 
0.8 
0.6 
0.1 
1.3 
1.0 
2.5 
0.6 
0.5 
0.4 

Per  cent 

8.5 
7.8 
10.2 
12.4 
8.6 
11  .4 
10.2 
4.5 
13.8 
15.0 
20.1 
12.6 
13.1 
7.7 

Qoat                              

Mare 

Sow    

Camel  

Hippopotamus  

Bitch  

Cat  

Rabbit  

Elephant                 

Porpoise                  

Whale  ...                  ... 

operation  of  milking  and  during  subsequent  exposure  to  the  air, 
bacteria,  molds  and  yeasts  find  admission.  They  may  find  their 
way  into  the  milk  from  the  hands  of  the  milker,  the  teats  anc 
hair  of  the  cow,  and  often  from  the  vessel  in  which  the  milk  is 
collected.  The  ordinary  souring  of  milk  is  produced  by  various 
species  of  bacteria,  which  during  their  growth  convert  the  milk- 
sugar  into  lactic  acid.  This  formation  of  acid  induces  the  curd- 
ling of  the  milk.  This  generally  occurs  when  the  amount  of  acid 
reaches  about  0.7  per  cent.  Curdling  is  produced  by  less  acid 
if  the  milk  is  heated. 

Other  organisms,  and  often  of  a  more  dangerous  character 


Milk  and  Its  Products.  270 

sometimes  find  their  way  into  milk.  Outbreaks  of  diarrhoea,  ty- 
phoid and  cholera  have  been  traced  to  contaminated  milk.  It  has 
also  been  shown  that  milk  can  act  as  a  carrier  of  tuberculosis. 
Milk,  too,  has  the  property  of  absorbing  gases  and  vapors  and  in 
consequence  readily  acquires  odors  and  flavors  from  the  air. 

All  these  facts  emphasize  the  necessity  of  cleanliness  in  milk 
production  and  precautionary  measures  to  check  bacterial  devel- 
opment should  the  milk  become  seeded.  Their  growth  can  be 
checked  by  cooling  the  milk  as  soon  as  it  is  produced.  This  pre- 
vents a  rapid  development  of  the  organisms  already  in  the  milk, 
but  will  not  entirely  prevent  their  development.  It  will  prolong 
the  sweetness  of  the  milk.  In  order  to  destroy  the  organisms 
which  have  gained  access  to  the  milk,  heating  or  the  use  of  anti- 
septics must  be  resorted  to.  Where  the  process  of  heating  is 
carried  on  at  a  temperature  high  enough  to  completely  destroy 
all  organisms  and  their  spores — a  process  known  as  sterilization 
and  requiring  a  temperature  above  100°  C. — undesirable  chem- 
ical changes  are  produced  in  the  milk.  The  sugar  is  turned 
brown,  the  albumin  partly  precipitated,  and  the  milk  acquires  a 
burnt  or  cooked  flavor.  To  avoid  these  disadvantages  the  process 
known  as  Pasteurization  is  often  substituted.  The  milk  is  heated 
to  only  60  to  80°  C.,  whereby  the  flavor  is  little  affected  and  most 
of  the  active  bacteria  are  killed.  The  keeping  qualities  are  thus 
materially  increased. 

Antiseptics.  By  adding  various  substances  to  milk,  the 
growth  of  micro-organisms  can  be  impeded,  if  not  entirely  pre- 
vented. When,  however,  such  quantities  of  an  antiseptic  are 
added  as  will  prevent  bacterial  growth,  then  there  is  little  doubt 
that  the  milk  is  made  unsuitable  for  human  consumption.  The 
chief  preservatives  in  common  use  are  boric  acid,  salicylic  acid, 
formaldehyde  and  benzoic  acid.  Their  use  in  any  quantity  is 
reprehensible,  allowing  uncleanly  methods  in  milk  production  to 
be  practiced,  as  well  as  endangering  the  health  of  the  consumer, 
and  should  be  absolutely  prevented. 


280  Agricultural  Chemistry. 

Products  derived  from  milk.  Cream.  The  fat  of  milk  exists 
in  globules  and  is  specifically  lighter  than  the  aqueous  portion  of 
the  milk.  This  makes  the  globules  tend  to  rise  to  the  surface, 
where  they  form  a  layer  of  cream.  The  specific  gravity  of  fat 
at  15°  C.  is  .930,  while  the  serum  in  which  the  globules  float  has 
a  specific  gravity  of  about  1.036.  The  globules  are  of  various 
sizes.  They  are  considerably  larger  in  the  milk  of  the  Jersey  and 
Guernsey  breeds  than  in  the  Ayrshire  and  Holstein  breeds.  The 
Devons  and  Shorthorns  hold  an  intermediate  position.  The 
smaller  the  globule,  the  larger  is  its  surface  in  proportion  to  its 
volume,  and  the  greater  the  resistance  to  its  rise.  For  this  reason 
Jersey  milk  creams  easier  than  that  from  breeds  with  smaller 
globules. 

Cream  can  be  separated  from  milk  by  gravitation  or  by  sub- 
stituting for  gravity  the  much  greater  force  produced  by  raptd 
rotation.  When  milk  leaves  the  cow  it  will  have  a  temperature 
of  about  90°  F.,  and  where  set  for  cream  should  be  cooled  as 
quickly  as  possible.  There  are  two  methods  in  use  for  the  separ- 
ation of  cream  by  the  gravity  processes,  namely,  shallow  setting 
and  deep  setting.  In  the  former  the  milk  is  placed  in  shallow 
vessels  to  a  depth  of  2  to  4  inches,  cooled  to  about  60°  F.  and 
kept  at  that  temperature  for  24  or  36  hours.  The  cream  layer 
is  then  removed  by  a  shallow  spoonlike  vessel,  or  sometimes  by 
running  off  the  milk  into  another  vessel  through  a  hole  at  the 
bottom  of  the  creaming  pan.  Under  these  conditions  of  cream- 
ing a  large  surface  is  exposed,  the  milk  may  receive  a  great  num- 
ber of  bacteria,  and  decomposition  of  a  part  of  the  protein  and 
sugar  may  rapidly  take  place.  The  cream  obtained  in  this  way 
is  liable  to  be  contaminated  with  various  strongly  flavored  pro- 
ducts of  decomposition,  resulting  in  a  poor  quality  of  butter. 
The  process  is  not  efficient,  as  only  about  80  per  cent  of  the  milk 
fat  is  removed. 

By  the  deep-setting  system,  the  milk,  while  still  warm,  is 
placed  in  cylindrical  vessels,  usually  about  8  to  12  inches  in 


Milk  and  Its  Products.  281 

diameter  and  15  to  20  inches  deep,  which  are  then  immersed  in 
ice-cold  water.  The  cream  rises  quickly  and  the  process  will  be 
practically  complete  in  12  hours.  By  this  process  90  to  95  per 
cent  of  the  fat  can  be  removed,  dependent  upon  conditions  of 
cooling,  manipulation,  and  the  breed  of  the  cow.  It  has  been 
found  that  by  .this  process  twice  as  much  fat  remains  in  the  skim 
milk  from  Holstein  cows  as  in  that  from  Guernseys  and  Jerseys, 
owing  to  the  slower  rising  of  the  small  fat  globules  in  Holstein 
milk. 

Many  explanations  of  the  efficiency  of  this  system  have  been 
attempted.  Since  fat  expands  and  contracts  with  changes  of 
temperature  more  rapidly  than  does  water,  the  effect  of  cooling 
upon  milk  would  be  to  lessen  the  difference  in  specific  gravity 
between  fat  and  water ;  it  would  also  increase  the  viscosity  of  the 
milk,  both  conditions  working  against  a  rapid  rise  of  the  fat 
globules.  Perhaps  the  most  satisfactory  explanation  is  the  one 
given  by  Doctor  Babcock.  There  exists  in  milk  a  substance  sim- 
ilar in  character  to  blood  fibrin,  which,  when  formed  produced 
more  or  less  of  a  network  throughout  the  body  of  the  milk.  By 
rapidly  cooling  the  milk,  the  formation  of  fibrin  threads  is 
checked.  This  allows  the  fat  globules  a  free  path  of  movement, 
with  the  resultant  rapid  formation  of  the  cream  layer.  The  ex- 
istence of  fibrin  in  milk  has  been  definitely  proven. 

Separators.  A  third  plan  of  separating  cream  is  by  subject- 
ing the  milk  to  extremely  rapid  horizontal  revolution  in  a  cen- 
trifugal machine.  Under  this  condition  the  serum,  being  the 
constituent  of  heaviest  specific  gravity,  is  thrown  to  the  outer 
side  of  the  revolving  vessel  while  the  fat  globules  rise  into  the 
center  of  the  mass.  The  milk  should  be  warmed  to  about  85°  F. 
previous  to  separating,  for  the  purpose  of  lowering  its  viscosity. 
By  providing  suitable  outlets,  the  skim  milk  can  be  directed  into 
one  channel  and  the  cream  into  another.  By  adjusting  the  size 
of  one  of  these  openings,  thick  or  thin  cream  can  be  obtained  at 
will.  Both  the  cream  and  skim  milk  thus  obtained,  are,  of  course, 
perfectly  sweet.  The  separation  of  the  fat  is  far  more  complete 


282  Af/riruUural  Chemistry. 

than  by  either  of  the  other  processes,  from  97  to  98  per  cent 
being  recovered  in  a  good  machine. 

^Composition.  Cream  varies  enormously  in  composition,  the 
proportion  of  fat  varying  from  as  low  as  10  per  cent  to  as  high 
as  60  or  70  per  cent.  By  shallow  setting,  a  product  containing 
Irom  15  to  40  per  cent  is  usually  obtained;  at  low  temperatures 
about  20  per  cent  of  fat  is  usually  present.  In  the  deep-setting^ 
process  the  cream  obtained  will  contain  about  20  to  25  per  cent 
of  fat.  Cream  separated  by  the  centrifugal  process  will  vary 
according  to  the  mode  of  working.  It  may  be  quite  poor,  or  it 
may  contain  50  to  60  per  cent.  Generally  speaking,  thin  cream 
will  contain  15  to  25  per  cent  of  fat,  and  thick  cream  30  to  50 
per  cent  of  fat. 

Devonshire-'  *  clotted  cream"  is  prepared  by  setting  the  milk 
in  shallow  pans  and  at  a  fairly  cool  temperature  for  12  hours. 
It  is  then  heated  to  a  temperature  of  70  to  80°  C.  until  the  surface 
becomes  sharply  wrinkled.  It  is  then  set  in  the  cold  for  12  hours 
and  skimmed.  Such  clotted  cream  usually  contains  about  58 
per  cent  of  fat,  34  per  cent  of  water  and  about  8  per  cent  of 
solids  not  fat. 

Skimmed  milk  varies  in  composition  according  to  the  more  or 
less  complete  removal  of  the  fat.  Milk  thoroughly  skimmed 
after  shallow  setting  will  contain  about  1  per  cent  of  fat.  With 
deep  setting  and  ice,  the  per  cent  of  fat  left  in  the  milk  will  vary 
from  0.15  to  0.40.  When  the  centrifugal  machine  has  been  used 
the  percentage  will  be  from  .05  to  .15.  Milk  of  average  quality 
may  be  expected  to  yield  with  a  good  centrifugal  machine,  skim- 
med milk  of  about  the  following  composition  :— 

Per  cent 

Water 90.54 

Fat 0.10 

Sugar 4.94 


Per  cent 

Casein  3.11 

Albumin 0.42 

Ash,  etc 0.89 


Skimmed  milk  contains  a  valuable  amount  of  food  stuffs,  and 
should  be  utilized  on  the  farm  for  feeding  pigs  or  in  other  ways. 
Though  poorer  in  fat,  machine  separated  milk  has  the  advantage 


Milk  and  Its  Products.  283 

of  being  sweet  and  of  keeping  better  than  the  product  from  other 
processes  of  skimming. 

Butter.  When  cream  or  milk  is  agitated  for  some  time,  the 
fat  globules  coalesce  and  butter  separates  out  in  irregular  masses. 
While  these  masses  are  not  continuous  fat,  very  few  of  the 
original  globules  remain.  The  spherical  globules  visible  in  but- 
ter under  the  microscope  consist  of  minute  drops  of  butter-milk 
or  water,  enclosed  in  the  fat. 

Churning  is  a  mechanical  process.  The  fat  globules  collide, 
adhere,  and  the  large  irregular  masses  thus  formed  become  cen- 
ters of  growth,  to  which  other  fat  globules  adhere.  Portions  of 
the  aqueous  liquid,  butter-milk,  are  enclosed  in  the  masses  of  fat. 
During  the  "working"  of  the  butter,  the  butter-milk  is  partly 
pressed  out.  For  butter  to  be  of  good  quality,  it  must  possess 
a  certain  texture  and  grain  and  be  neither  hard  nor  greasy.  This 
desirable  result  can  only  be  attained  by  careful  churning  at  a 
favorable  temperature.  If  the  temperature  of  the  cream  is  too 
low  the  butter  will  be  long  in  coming  and  will  be  hard  in  texture. 
If  the  temperature  is  too  high,  the  butter  will  come  very  speed- 
ily, but  the  product  will  be  greasy  and  destitute  of  grain.  No 
temperature  can  be  fixed  as  the  best  at  which  churning  should 
always  take  place.  The  proportion  of  solid  and  liquid  fats  in 
the  milk  varies  somewhat  with  the  breed  and  feed  of  the  cow, 
and  this  necessitates  a  change  in  the  temperature.  From  45  to 
65°  F.  is  the  greatest  range  usually  employed  and,  in  most  cases 
from  50  to  60°  F.  is  chosen.  "Kipened"  or  sour  cream  must 
be  churned  at  a  higher  temperature  than  that  required  for  sweet 
cream.  The  exact  temperature  most  suitable  for  churning  may 
be  ascertained,  by  recording  every  day  the  temperature  employed, 
the  length  of  time  occupied  in  churning  and  the  character  of  the 
product.  When  this  is  done  the  experience  gained  can  be  used 
in  selecting  the  most  suitable  temperature. 

The  temperature  may  rise  during  churning,  work  being  con- 
verted into  heat.  This  causes  an  expansion  of  the  air  in  the 
churn.  In  addition,  the  carbon-dioxide  in  solution  in  the  serum 


284  Agricultural  Chemistry. 

of  a  ripened  cream  is  driven  out  by  the  agitation.  These  two 
factors  give  rise  to  the  pressure  observed  within  the  churn. 
Churning  should  always  be  stopped  as  soon  as  the  butter  appears 
in  fine  grains.  This  allows  a  more  complete  separation,  by  wash- 
ing, of  the  butter-milk,  and  removes  one  of  the  important  factors 
in  the  production  of  mottles  in  butter.  Further,  the  more  com- 
pletely the  butter-milk  is  removed,  the  better  will  be  the  keeping 
qualities  of  the  butter. 

Freshly  separated  cream  is  sometimes  churned,  but  it  is  gen- 
erally admitted  that  the  best  flavor  and  aroma  for  butter  can 
only  be  obtained  by  the  use  of  properly  ripened  cream.  This  is, 
cream  to  which  lactic  acid  organisms  have  either  gained  access 
spontaneously,  or,  as  is  preferred  in  modern  practice,  have  been 
added  in  the  form  of  a  ''starter"  of  sour  skimmed  milk  or  some 
pure  culture  of  the  lactic  organisms.  The  degree  of  ripeness 
which  is  probably  best,  corresponds  to  about  0.5  per  cent  of  lactic 
acid ;  but  the  acidity  most  suitable  depends  to  some  extent  upon 
the  flavor  desired  in  the  butter.  If  the  cream  is  over  ripe,  the 
casein  present  may  be  hardened  and  on  churning  is  found  as 
white  specks  or  flakes  in  the  butter,  spoiling  its  appearance  and 
endangering  its  keeping  qualities. 

Salt  is  usually  added  to  butter,  serving  both  as  a  condiment 
and  as  a  preservative,  the  proportion  varying  from  a  mere  trace 
to  5  or  6  per  cent. 

Composition  of  butter.  The  main  constituent  is  of  course 
fat,  but  in  addition,  water,  casein,  milk  sugar  and  ash  are  also 
present.  The  amount  of  fat  is  usually  about  80  to  86  per  cent, 
water  about  11  to  12,  casein  from  0.6  to  1.5  and  salt  from  0.1 
to  4.0  per  cent.  Under  the  present  pure  food  law  of  the  United 
States  it  is  unlawful  to  sell  butter  containing  more  than  16 
per  cent  of  water.  So  called  "milk-blended  butters "  prepared 
by  kneading  butter  in  milk,  usually  contain  an  excessive  quantity 
of  water  and  a  high  proportion  of  casein. 

Renovated  butter.  In  this  country  old  and  rancid  butter  is 
sometimes  converted  into  what  is  known  as  " renovated, "  "pro- 


Milk  and  Its  Products.  285 

cess,"  or  "aerated"  butter.  This  is  done  by  melting  the  butter, 
separating  the  fat  from  the  casein,  water,  etc.,  blowing  air 
through  the  fat  to  remove  the  unpleasant  odors,  and  then  churn- 
ing the  liquid  fat  with  milk  until  an  emulsion  is  formed.  This 
is  then  quickly  cooled  in  ice  and  a  granular  mass  results.  It  is 
then  worked,  salted,  and  made  up  as  butter. 

Oleomargarine  is  also  known  as  " margarine"  or  "butterine. " 
This  product,  which  is  intended  as  a  substitute  for  butter,  is 
made  by  churning  so  called  ' '  oleo  oil ' '  with  lard,  milk,  sometimes 
a  little  butter,  and  occasionally  cotton-seed  oil  or  peanut  oil,  in 
a  warm  state.  After  the  churning  the  mixture  is  quickly  cooled, 
salted  and  "worked."  Where  coloring  matters  are  used,  with 
the  intention  of  imitating  butter,  a  tax  of  10  cents  a  pound  is 
imposed.  On  uncolored  "oleo"  a  tax  of  %  cent  per  pound  is 
levied. 

The  "oleo  oil"  is  made  from  beef  fat  by  melting,  carefully 
clarifying,  and  allowing  it  to  stand  at  a  temperature  of  about 
30°  C.  The  semi-solid  mass  which  results  is  then  separated  by 
a  press  into  solid  stearin  and  a  liquid  composed  of  olein  and 
palmitin. 

Pure  butter  can  be  distinguished  from  "renovated"  butter 
and  from  "oleo"  by  its  behavior  when  heated  in  a  test  tube  or 
spoon  over  a  flame.  Oleomargarine  and  renovated  butter  boil 
with  much  sputtering  and  produce  no  foam,  or  very  little,  while 
genuine  butter  in  boiling  produces  more  foam  and  less  noise. 

Butter-milk.  The  liquid  remaining  in  the  churn  after  the 
separation  of  butter  from  the  cream  varies  a  good  deal  in  com- 
position. With  good  churning  of  ripened  cream,  the  percentage 
of  fat  in  the  butter-milk  may  be  0.3  or  less.  When  sweet  cream 
is  churned  1.0  per  cent  of  fat  may  be  expected.  The  average 
composition  of  butter-milk  will  be  about  as  follows: — Water, 
90.9  per  cent ;  proteins,  3.5 ;  fat,  0.5 ;  sugar  and  lactic  acid,  4.4 ; 
ash,  0.7.  The  chief  use  for  butter-milk  has  been  as  food  for  pigs, 
but  there  is  a  growing  demand  for  it  as  human  food.  The  finely 


286 


Agricultural  Chemistry. 


divided  condition  of  its  protein  makes  it  readily  and  easily  di- 
gestible. The  preparation  of  a  new  product,  butter-milk  cream, 
will  probably  increase  the  consumption  of  this  material  as  human 
food.  This  product  is  prepared  by  holding  the  butter-milk  at  75 
to  78°  F.  for  about  2  hours,  and  finally  heating  to  130  to  140°  P. 
for  a  short  time.  This  treatment  induces  an  aggregation  of  the 
finely  divided  protein,  allowing  the  material  to  be  strained  and, 
collected,  which  otherwise  could  not  be  done. 

The  following  table  shows  how  the  various  constituents  of  100 
pounds  of  milk  are  distributed  when  the  milk  is  creamed  and 
made  into  butter: — 

Distribution  of  Milk  Solids  in  Butter  Making. 


Products  from  100  Ibs.  of  milk,  in  Ibs. 

100  Ibs. 
of  milk 

20  Ibs. 
of  cream 

Skimmed 
milk 

Butter 

Butter 
milk 

Total  solids.. 
Fat  .... 

13.00 
4.00 
3.50 
4.75 
0.75 

5.18 
3.88 
0.50 
0.75 
0.05 

7.82 
0.12 
3.00 
4.00 
0.70 

4.00 
3.83 
0.10 
0.05 

1.18 
0.05 
0.40 
0.70 
0.03 

Casein  and  albumin 
Sugar  and  acid  
Ash 

The  4  pounds  of  solid  matter  recovered  in  the  butter,  which 
contains  3.83  pounds  of  fat,  together  with  the  salt  and  water 
present,  make  about  4.6  pounds  of  marketable  butter. 

Condensed  milk  and  milk  powders.  Condensed  milk  is  pre- 
pared by  evaporating  milk  in  vacuum  pans  until  its  volume  is 
reduced  to  about  one-third  or  one-fourth  of  the  original,  and 
then  sealing  the  condensed  product  while  hot.  In  many  brands 
cane  sugar  is  added  in  large  proportion.  This  aids  in  preserving 
the  product,  even  after  the  cans  are  opened.  To  other  brands, 
often  known  as  "evaporated  cream,"  no  sugar  is  added. 

The  composition  of  these  products  varies,  the  fat  being  liable 


Milk  and  Its  Products.  287 

to  considerable  variation.     The  following  analysis  may  be  taken 
as  typical:— 

Sweetened  Unsweetened 

Per  cent  Per  cent 

Water 25.7  71.7 

Fat 10.7  8.1 

Protein 8.5  8.7 

Milk  sugar 11.9  9.9 

Cane  sugar 41.9  .... 

Ash !.:•',  1.6 

Milk  powders  are  made  by  several  processes.  One  of  the 
earliest  was  to  evaporate  the  milk  in  a  thin  layer,  on  a  heated 
revolving  drum.  By  this  process  the  evaporation  of  water  takes 
place  rapidly  and  the  dried  film  of  milk  drops,  or  is  scraped, 
from  the  rolls,  appearing  as  a' thin  yellow  scale.  Another  proc- 
ess, of  recent  date,  consists  of  atomizing  the  milk  under  pressure 
into  a  moving  volume  of  warm  dry  air.  The  moisture  is  in- 
stantaneously absorbed  and  by  the  use  of  centrifugal  force,  the 
vapor  charged  air  is  made  to  give  up  the  minute  particles  of 
suspended  matter.  The  product  is  a  fine  flour,  possessing,  in 
common,  with  some  other  brands  prepared  by  other  methods, 
the  properties  of  milk  when  again  stirred  up  in  water.  There 
are  preparations  on  the  market  which  do  not  have  these  prop- 
erties, probably  because  they  have  been  subjected  to  too  high 
heat  in  the  drying  process. 

Of  the  several  milk  powders  examined  by  the  authors,  only 
one  contained  any  appreciable  quantity  of  fat.  It  appears  that 
most,  if  not  all  of  these  powders  are  prepared  from  skimmed,  or 
partially  skimmed  milk.  This  is  probably  necessary,  in  order 
that  dessication  may  be  more  complete  and  the  keeping  qualities 
of  the  product  well  insured.  One  product  examined,  and  rep- 
resented as  a  preparation  from  whole  milk,  contained  but  9  per 
cent  of  fat.  A  milk  powder  prepared  from  average  whole  milk 
should  contain  at  least  25  per  cent  of  fat. 

Various  other  dry  foods  are  prepared  from  the  casein  of  milk, 


288  Agricultural  Chemistry. 

among  which  are  "plasmon"  and  "nutrose. "  "Plasmon"  is 
made  by  treating  the  curd  of  skimmed  milk  with  sodium  bi- 
carbonate and  drying  the  thoroughly  mixed  product  in  an  at- 
mosphere of  carbon-dioxide.  "Nutrose"  is  also  a  sodium  com- 
pound of  casein. 

Cheese.  The  principal  varieties  of  commercial  cheese  are  pre- 
pared from  milk  by  the  action  of  rennet.  Rennet  is  made  by 
extracting  the  fourth  stomach  of  the  calf  with  a  5  to  10  per  cent 
solution  of  common  salt.  Its  power  to  coagulate  milk  is  due  to 
the  presence  of  an  enzyme  called  rennin,  which  plays  a  similar 
part  in  the  process  of  digesting  milk  in  the  calf 's  stomach.  Ren- 
nin coagulates  the  casein  of  the  milk,  forming  a  curd  which 
mechanically  entangles  almost  all  the  fat  of  the  milk,  leaving 
the  albumin  and  sugar  in  the  whey.  Rennin  acts  more  rapidly 
at  about  102  to  104°  F.  In  cold  milk  it  is  slow  in  its  action, 
while  at  temperatures  above  120°  F.  it  is  retarded,  its  action  en- 
tirely ceasing  at  130°  F.  In  milk  containing  some  acid,  but  not 
enough  to  curdle  it,  rennin  action  is  hastened. 

It  is  impossible  in  a  work  of  this  scope  to  describe  the  varieties 
of  cheese  and  their  methods  of  manufacture. 

The  common  practice  followed  in  the  preparation  of  American 
cheddar  cheese  is  to  "ripen"  the  milk  to  an  acidity  correspond- 
ing to  about  0.25  per  cent  of  lactic  acid.  This  is  done  by  adding 
to  it  a  starter  consisting  of  sour  milk  or  a  pure  culture  of  lactic 
organisms.  The  necessary  rennet  is  then  added,  the  milk  being 
previously  warmed  to  82  to  85°  F.  After  the  curd  is  sufficiently 
firm,  requiring  about  30  minutes,  it  is  cut  into  cubes  and  the 
temperature  of  the  vat  raised  to  100°  F.  It  is  maintained  at 
that  temperature  for  1  to  2  hours,  during  which  time  the  curd 
shrinks  and  the  acidity  increases.  After  proper  acidity  is  de- 
veloped, the  whey  is  drawn,  the  curd  piled  in  one  end  of  the  vat 
and  kept  warm.  In  this  condition  it  mats  into  a  solid  mass.  It 
is  finally  passed  through  a  grinding  mill,  salted,  and  pressed  into 
molds.  The  cheese  is  then  placed  in  a  curing  room  at  a  tem- 
perature of  50  to  60°  F.  and  allowed  to  ripen.  A  lower  tern- 


M ilk  and  Its  Products. 


289 


perature  than  this  can  be  used,  with  great  improvement  in  the 
quality  of  the  product.  In  the  manufacture  of  Swiss  cheese  the 
milk  must  be  in  a  sweet  condition.  No  acid  is  developed  and  the 
curd  is  cooked  at  a  temperature  of  125  to  130°  F.  The  curd  is 
placed  in  molds  and  the  salting  done  by  surface  application.  In 
making  soft  cheese  the  curd  is  not  cut  or  pressed,  but  simply 
allowed  to  drain  on  a  cloth  or  frame. 

Reckoning  that  the  fresh  cheese  which  goes  into  the  cheese 
room  contains  about  36  per  cent  of  water,  the  products  from  100 
Ibs.  of  normal  milk  will  be  as  follows: — 

Products  from  100  Lbs.  of  Normal  Milk. 


Total 
product 

Water 

Protein 

Fat 

Sugar 

Ash 

Milk  

Lbs. 
100.0 

Lbs. 
87.10 

Lbs. 
3  40 

Lbs. 
3.90 

Lbs. 

4.85 

Lbs. 

7.5 

Cheese  

10.40 

3.94 

2.57 

3.59 

0.17 

0.13 

Whey  

89  60 

83.16 

0.83 

0.31 

4.68 

0.62 

Ripening.  Cheddar  cheese  ripens  quickest  at  a  moderately 
warm  temperature,  50  to  60°  F.  being  usually  employed.  It  has 
been  shown  that  it  will  also  ripen  at  a  much  lower  temperature — 
even  at  30°  F. — and  the  product  will  be  of  excellent  quality.  The 
time  of  ripening  is  necessarily  longer  when  conducted  at  the 
'lower  temperature.  During  this  curing  process  many  complex 
changes  occur.  The  sugar  is  converted  to  lactic  acid,  some  water 
evaporates,  and  the  insoluble  proteins  are  partly  converted  into 
water  soluble  products.  Ammonium  compounds  are  also  pro- 
duced during  the  ripening  process.  Experiments  have  shown 
that  fresh  cheddar  cheese  contains  but  from  5  to  10  per  cent  of 
its  protein  in  water  soluble  form,  while  at  the  end  of  5  months, 
35  to  40  per  cent  will  be  found  in  that  form.  These  changes,  ac- 
cording to  one  view,  are  produced  primarily  by  the  lactic  acid 
organisms.  Another  theory  ascribes  them  to  enzymatic  action, 
the  enzymes  being  galactase,  which  is  present  in  all  milks  and 


290 


.  1  (jricultv rn I  ( 'hemistry. 


possesses  the  power  of  peptonizing  casein,  and  pepsin,  contained 
in  the  rennet  extract  used.  Whatever  may  be  the  cause  of  these 
changes,  there  can  be  no  doubt  that  during  the  curing  process 
the  flavor  and  aroma  are  developed  and  that  a  considerable  por- 
tion of  the  insoluble  nitrogenous  bodies  are  converted  into  water- 
soluble  forms.  The  fat  of  cheese  undergoes  slight  change  during 
ripening,  a  small  proportion  of  the  neutral  fat  being  decomposed 
and  butyric  and  other  fatty  acids  formed.  The  sugar  which  was 
present  when  the  cheese  was  first  made  also  disappears  after  a 
period  of  7  to  10  days.  Lactic  acid  is  the  main  product  formed 
from  the  sugar,  although  other  products,  probably  of  great  im- 
portance to  flavor  development,  are  produced. 

The  ripening  of  special  kinds  of  soft  cheese,  such  as  Roquefort 
and  Camembert  is  attributed  to  such  special  ferments  as  molds, 
introduced  during  the  process  of  manufacture.  The  average 
composition  of  various  cheeses  is  given  in  the  following  table  :— 

Composition  of  Cheese. 


Water 

Protein 

Fat 

Ash 

Cheddar 

Per  cent 
34  4 

Per  cent 

2fi  4 

Per  cent 

qo   7 

Per  cent 

o    a 

Cheshire  

32  6 

32  5 

9(}  0 

4  3 

Swiss  

35  8 

24  4 

37  4 

2  4 

£dam 

36  3 

24  1 

Q(\  o 

4  Q 

Roquefort 

31  2 

27  H 

QQ    0 

60 

Brie..     . 

50  4 

17  2 

oc;   1 

K.    A 

Limburg  

35  6 

28  5 

29  8 

5  9 

Under  the  United  States  pure  food  act,  the  following  defini- 
tions of  cheese  were  established. 

(1)  Whole  milk  or  full  cream  cheese  is  cheese  made  from  milk 
from  which  no  portion  of  the  fat  has  been  removed. 

(2)  Skim  milk  cheese  is  cheese  made  from  milk  from  which 
any  portion  of  the  fat  has  been  removed. 

(3)  Cream  cheese  is  cheese  made  from  milk  and  cream  or  milk 
containing  not  less  than  6  per  cent  of  fat. 


Milk  and  Its  Products.  291 

Standard.  Whole  milk  or  full  cream  cheese  contains,  in  the 
water-free  substance,  not  less  than  50  per  cent  of  butter  fat. 

The  term  "full  cream"  simply  means  that  in  the  manufacture, 
whole  milk  has  been  used.  It  gives  the  impression  that  cream 
has  been  added,  but  such  is  not  the  case. 

In  some  cases,  cheese  is  adulterated  by  the  addition  of  foreign 
fat,  as  lard.  Such  cheese  is  usually  known  as  "filled"  cheese. 

Whey.  As  already  stated,  whey  contains  almost  all  of  the 
milk  suga.r  and  albumin  originally  present  in  the  milk,  as  well 
as  a  portion  of  the  ash.  The  amount  of  fat  in  the  whey  will  de- 
pend upon  the  treatment  the  curd  has  received.  If  the  milk  has 
been  rich,  the  temperature  of  cooking  high,  and  the  curd  roughly 
handled,  considerable  quantities  of  fat  will  be  present.  Where 
whey  is  rich  in  fat,  it  is  customary  to  recover  it  for  the  manu- 
facture of  whey  butter,  either  by  allowing  it  to  rise  by  gravitj^ 
or  through  the  use  of  the  separator.  The  average  composition 
of  whey  is  about  as  follows :  Water,  93.3  per  cent ;  protein,  0.9 : 
fat,  0.3 ;  sugar,  4.9 ;  ash,  0.6. 

The  cheese  yield  of  milk.  As  has  been  seen,  the  two  milk  con- 
stituents that  must  determine  the  yield  of  cheese  are  casein  and 
fat.  The  percentage  of  these  varies  in  milks  from  different  in- 
dividual cows.  They  are  not  always  in  the  same  relation  in  two 
different  milks.  Milks  of  high  fat  content  are  not  proportionately 
richer  in  casein  than  milks  of  low  fat  content.  As  a  rule,  for 
100  pounds  of  fat  in  Jersey  and  Guernsey  milk,  one  may  expect 
55  to  65  pounds  of  casein,  while  in  the  milk  from  the  Ayrshire 
and  Holstein  breeds,  there  will  be  65  to  75  pounds.  There  will 
be  individual  exceptions  to  this  general  statement. 

In  herd  milks,  although  the  relation  of  casein  to  fat  is  more 
constant,  nevertheless  variations  in  the  proportion  of  these  two 
constituents  exist.  The  general  rule  that  high  fat  milks  do  not 
yield  in  proportion  to  their  fat,  as  much  cheese  as  low  fat  milks, 
finds  its  explanation  in  the  fact  that  high  fat  milks  have  pro- 
portionately less  casein.  This  is  illustrated  in  the  following 


292 


Agricultural  Chemistry. 


table,  which  represents  some  work  done  by  Babcock  at  a  number 
of  Wisconsin  cheese  factories. 

Relation  of  Composition  of  Milk  to  Cheese  Yield. 


No.  of 
groups 

No.  of 
reports 

Range 
of  fat 

Average 
per  cent 
of  fat 

Average 
yield  of 
cheese  per 
100  Ibs.  milk 

Lbs.  of 
cured  cheese 
for  1  Ib.  fat 

1 

'  24 

Under  3.  25 

3.12 

9.19 

2.94 

2 

90 

3.25-3.50 

3.38 

9.28 

2.73 

3 

134 

3.50-3.75 

3.60 

9.40 

2.61 

4 

43 

3.75-4.00 

3.83 

9.80 

2.56 

5 

46 

4  00-4.25 

4.09 

10.30 

2.51 

6 

20 

Over  4.  25 

4.44 

10.70 

2.40 

It  will  be  seen  that  the  yield  of  cheese  in  proportion  to  the 
fat  is  less  in  the  rich  milks  than  in  the  poorer  milks.  A  milk 
testing  6  per  cent  of  fat  will  not  make  twice  as  much  cheese  as 
one  testing  3  per  cent. 

Making  out  dividends  at  cheese  factories.  While  the  inequal- 
ity of  the  cheese-yielding  capacity  of  milks,  and  of  the  distribu- 
tion of  dividends,  based  on  their  fat  content  alone,  has  been 
recognized,  it  has  been  quite  generally  asserted  that  such  in- 
equality disappeared  because  of  the  improved  quality  of  the 
product  made  from  the  milks  of  higher  fat  content.  This  is  true 
when  we  consider  cheese  made  from  skimmed  or  partly  skimmed 
milk  and  from  milk  very  rich  in  fat  or  re-inforced  with  cream. 
But  within  the  range  of  normal  factory  milk  testing  in  fat  from 
3  to  4^/2  per  cent,  the  quality  of  the  product,  as  judged  by  buyers 
for  the  market,  does  not  show  uniform  improvement  with  increase 
of  fat  in  the  milk.  This  has  been  shown  by  the  work  of  the 
Canadian  Experiment  Station  at  Guelph  and  by  the  Wisconsin 
Station.  No  grading  in  the  price  of  cheese,  made  from  normal 
whole  milk,  based  on  its  fat  content,  is  at  present  practiced. 
Other  factors,  as  the  sanitary  condition  of  the  milk  from  which 
the  cheese  is  made  and  the  subsequent  ripening  processes,  play 
an  important  part  in  determining  the  quality  of  the  product. 


Milk  and  Its  Products.  293 

Normal  factory  milks  may  vary  in  their  cheese-yielding  capac- 
ity, and  the  quality  of  the  product  from  such  milks  is  not  deter- 
mined by  those  variations  that  may  occur  in  the  fat  and  casein 
content.  It  is  clear  that  the  most  complete  and  equitable  method 
for  the  distribution  of  dividends  at  a  cheese  factory,  is  to  allow 
for  the  amounts  of  both  fat  and  casein  delivered  by  the  patron. 

In  its  simplest  form  this  consists  in  allowing  equal  values  for 
both  the  fat  and  the  casein,  the  amounts  of  which  can  be  de- 
termined by  methods  applicable  to  factory  conditions.  Such 
tests  are  the  Babcock  fat  test  and  the  mechanical  casein  test 
devised  by  one  of  the  authors.  A  patron  delivering  100  pounds 
of  milk,  containing  3.5  per  cent  of  fat,  and  2.4  per  cent  of  casein, 
should  be  paid  on  the  basis  of  5.9  pounds  of  cheese  solids  deliv- 
ered. The  price  per  pound  of  cheese  solids  would  be  determined 
by  the  price  received  for  the  cheese  in  the  market. 


CHAPTER  XIII 
INSECTICIDES  AND   RELATED   SUBSTANCES. 

A  number  of  miscellaneous  substances  used  in  the  agricultural 
industries  depend  primarily  upon  their  chemical  composition  for 
effectiveness.  Prominent  among  these  substances  are  various 
preparations  for  the  control  or  suppression  of  parasitic  pests 
upon  plants  and  animals  and  the  restriction  of  contagious  dis- 
eases. Brief  consideration  will  be  given  here  to  the  composition 
and  action  of  the  more  important  of  these  substances.  For  their 
practical  applications,  reference  should  be  made  to  special  books 
and  bulletins  on  these  subjects. 

The  following  classification  of  these  substances  will  be  followed 
for  the  sake  of  order  and  convenience:— 
I.     Insecticides. 
II.     Fungicides. 

III.     Disinfectants,  deodorants  and  antiseptics. 
IV.     Incidental  materials. 

Insecticides  are  substances  used  for  destruction  of  insects  feed- 
ing upon  the  fruit,  foliage  or  bark  of  vegetation  and  for  the  re- 
moval of  ticks  and  similar  pests  from  animals.  These  materials 
have  won  general  recognition  as  essential  factors  in  the  produc- 
tion of  high  grade  fruit. 

They  may  be  classed  as  stomachic,  contact,  or  gaseous  poisons. 
according  to  their  mode  of  action.  Such  insects  as  the  codling 
moth  of  the  apple  and  the  "potato  bug,"  which  are  surface  feed- 
ers, may  be  reached  by  poisons  of  the  first  class ;  the  aphides  or 
plant  lice  and  other  sucking  insects  must  be  attacked  by  poisons 
of  the  second  class;  and  the  resistant  scale  insects  and  other 
pests  are  most  efficiently  destroyed  by  fumigation  with  a  poison- 
ous gas. 

Stomachic  poisons  for  insects  are  generally  dependent  upon 
for  their  poisonous  effects.     Arsenic  does  not  enter  those 


Insecticides  and  Related  Substances.  295 

substances  as  the  free  element,  but  as  a  constituent  of  "white 
arsenic,"  technically  called  "arsenious  oxide"  or  "arsenious 
acid."  Soluble  compounds  of  arsenic  were  at  first  tested  as  in- 
secticides, but  they  were  found  to  cause  serious  injury  to  foliage. 
Later  experiments  have  demonstrated  that  arsenical  compounds 
insoluble  in  water  produced  the  desired  effect,  probably  by  virtue 
of  the  solvent  action  of  the  juices  of  the  digestive  tract  of  the 
insect.  The  resulting  effort  to  furnish  the  arsenic  of  insecticides 
in  insoluble  form  has  been  stimulated  also  by  the  passage  of  state 
laws  restricting  the  amount  of  arsenic  permissible  in  soluble  form. 
Paris  green  has  been  a  leading  insecticide  in  America  for  fifty 
years.  It  was  first  used,  apparently,  in  an  attempt  to  control 
the  Colorado  beetle  or  "potato  bug"  which  had  made  its  ap- 
pearance in  the  western  United  States.  This  stomachic  poison 
Contains  arsenious  acid,  acetic  acid  and  copper  in  a  definite  chem- 
ical structure  known  as  "Schweinfurt's  green,"  and  technically 
known  as  "copper  aceto-arsenite. "  It  is  prepared  by  adding  a 
hot  solution  of  arsenious  oxide  to  a  hot  solution  of  copper  acetate. 
Paris  green  separates  from  the  mixture  and  settles  out  as  a  rather 
fine  powder  of  a  clear,  green  color.  The  pure  compound  is  prac- 
tically insoluble  in  water,  but  readily  soluble  in  ammonium  hyd- 
roxide, or  ammonia  water,  and  has  the  following  composition: 

Per  cent 

Copper  oxide 31 . 29 

Arsenious  acid 58.65 

Acetic  acid 10.0(> 

Scorching  of  foliage  by  applications  of  Paris  green  suspended 
in  water  was  frequently  observed  during  its  early  use.  Gillettte 
showed,  in  1890,  that  the  use  of  lime  water  or  Bordeaux  mixture 
with  Paris  green  prevented  this  injury.  A  year  later,  Kilgore 
found  that  the  scorching  effects  were  due  to  soluble  forms  of 
arsenic  and  concluded  that  the  preventive  substances  acted  by 
virtue  of  their  lime,  which  fixed  the  soluble  arsenic  in  insoluble 
compounds.  Experiments  at  the  New  York  Experiment  Station 
with  Paris  green  and  sodium  arsenite  applied  to  potatoes  led  to 


29f>  Agricultural  Chemistry. 


: 


the  conclusions:  "That  Paris  green  is  not  injurious  to  pota 
foliage  if  applied  in  moderate  quantity  with  lime  water  or  B 
deaux  mixture  evenly  distributed;"  and  "That  sodium  arsenite 
should  not  be  applied  to  potatoes  except  with  Bordeaux  mix- 
ture." 

Adulteration  and  the  manufacture  of  impure  Paris  green  were 
more  or  less  prevalent  previous  to  the  passage  of  insecticide  laws. 
Gypsum  or  sulphate  of  lime  was  one  of  the  most  common  adulter- 
ants. This  has  little  if  any  insecticidal  value  and  was  added 
to  increase  the  bulk.  Other  impurities  may  result  from  the  use 
of  crude  materials  or  careless  methods  in  preparation.  Wood- 
worth  has  given  some  simple  tests  to  detect  common  forms  of 
adulteration. 

The  ammonia  test  is  performed  by  taking  an  amount  of  Paris 
green  that  can  be  held  on  a  five  cent  piece,  transferring  it  to  a 
drinking  glass  and  adding  about  six  tablespoonfuls  of  household 
ammonia  or  "spirits  of  hartshorn."  Keep  the  contents  of  the 
glass  well  stirred  for  five  minutes.  If  the  "green"  is  pure,  it 
will  then  form  a  clear,  dark-blue  solution  and  leave  no  solid 
residue.  If  gypsum  is  present,  it  will  form  a  white  suspension 
in  the  liquid  and  finally  settle  to  the  bottom  of  the  glass.  This 
is  not  a  conclusive  test  since  impurities  soluble  in'  ammonia  may 
be  present. 

The  glass  test  often  enables  one  to  distinguish  adulterated 
samples  not  detectable  by  ammonia.  Take  such  an  amount  of 
Paris  green  as  can  be  picked  up  readily  on  the  point  of  a  pen 
knife  and  place  it  on  a  small  rectangular  piece  of  clear  glass. 
Holding  the  glass  in  an  inclined  position,  gently  tap  the  lower 
edge  and  the  Paris  green  will  move  down  the  inclined  plane  leav- 
ing a  track  of  dust  behind.  In  the  case  of  a  pure  "green,"  the 
dust  will  be  of  a  bright  green  color.  If  the  sample  is  impure, 
it  may  leave  a  white,  pale-green  or  other-colored  streak,  depend- 
ing upon  the  color  of  the  adulterating  substance.  This  test  is 
best  used  for  comparing  unknown  samples  with  a  sample  known 
to  be  pure.  Like  the  ammonia  test,  it  is  not  infallible.  Varia- 


Insecticides  and  Related  Substances. 


297 


tions  in  the  color  of  samples  in  bulk,  especially  an  abnormally 
pale  shade,  and  a  tendency  to  dampness  or  lumping,  indicate 
almost  certain  adulteration. 

Microscopic  examination  offers  the  most  certain  and  satisfac- 
tory of  simple  methods  for  testing  the  purity  of  Paris  green. 
The  sample  is  prepared  for  this  test  as  in  the  " glass  test"  just 
described  and  the  dust  is  then  examined  under  a  medium  power 
objective.  The  Paris  green  will  be  seen  in  the  form  of  clean 


On  the  right — pure  Paris-green;    on  the  left — adulterated  Paris-green. 

round  balls ;  and  in  perfectly  pure  samples  these  are  all  that  can 
be  seen.  Impure  samples  will  exhibit  also  a  considerable  quan- 
tity of  material  of  crystalline  or  irregular  shapes,  and  usually 
white  in  color.  Excess  of  free  arsenious  oxide  is  not  so  readily 
distinguished  by  this  test.  When  mixed  with  the  prepared  Paris 
green  it  is  as  easily  recognized  by  the  microscope  as  is  any  other 
form  of  adulterant,  but  when  added  in  the  process  of  making, 
it  adheres  firmly  to  the  particles  of  true  green  and  causes  them 
to  stick  together  in  clusters. 

Chemical  analysis  is  the  only  absolute  means  of  determining 
the  purity  of  this  insecticide.  One  of  the  most  important  of  the 
chemical  determinations,  is  that  for  estimating  the  soluble  ar- 
senic in  Paris  green  and  other  insecticides.  Two  procedures  are 


298  Ai/rinilfnnil  Chemistry. 


in  use.  In  one  case  the  sample  is  extracted  with  a  hot  33  per  cent 
solution  of  sodium  acetate,  while  in  the  other  case  it  is  extracted 
for  several  days  with  cold  water  and  the  amount  of  arsenic  in 
solution  estimated.  The  former  method  apparently  shows  more 
nearly  the  amount  of  soluble  arsenic  that  may  be  present,  while 
the  latter  treatment  more  nearly  simulates  conditions  to  which 
the  insecticide  is  exposed  in  the  field. 

Control  laws  have  been  passed  by  some  suites  to  regulate  thr 
composition  and  sale  of  insecticides  as  lias  been  done  in  the  case 
of  commercial  fertilizers  and  feeding  stuffs.  In  some  cases,  spe- 
cial stipulation  is  made  with  regard  to  the  amount  of  free  ar- 
senious  oxide  permissible  in  Paris  green.  Idaho  allows  a  max- 
imum amount  of  six  per  cent  for  this  constituent  and  California 
allows  but  four  per  cent. 

Green  arsenoid  is  the  trade  name  for  a  compound  resembling 
Paris  green  in  composition  and  effects.  It  contains  no  acetic 
acid  but  is  formed  from  copper  oxide  and  arsenious  oxide,  and 
is  technically  known  as  copper  arsenite.  The  pure  compound 
contains  about  53  per  cent  of  arsenious  oxide.  Sodium  sulphate 
or  Glauber's  salt  is  a  by-product  in  the  process  of  preparation 
and  may  occur  together  with  sand  and  other  impurities  in  sueh 
an  insecticide;  they  should,  however,  be  present  in  only  small 
amounts.  The  following  data  from  an  analysis  of  green  arsenoid 
illustrates  the  relative  effect  of  sodium  acetate  solution  and  cold 
water  upon  Hie  ;irsenic  of  insecticides  : 

Free  areenious  acid  Per  cent 

(extracted  with  sodium  acetate)  .............  ........     3  23 

(extracted  with  cold  water)  .........................     5.88 

This  insecticide  has  given  excellent  results  when  mixed  with 
lime  to  "bind"  the  soluble  arsenious  oxide. 

London  purple  was  imported  from  England  by  Hessey  in  1^7^ 
as  a  substitute  for  Paris  green  in  destroying  the  potato  beetle. 
It  is  prepared  by  boiling  a  purple  residue  from  the  dye  industry. 
containing  free  arsrnious  ni-id.  with  slaked  lime.  Calcium  ar- 
senite is  formed  at  first,  but  by  -ul>se<|iient  hoilincr  and  exposure 


Insecticides  and  Related  Substances.  299 

to  the  air,  this  may  be  partly  oxidized  to  calcium  arsenate.  This 
insecticide  carries  some  impurities  brought  over  from  the  dye- 
making  process,  and  as  a  result  of  insufficient  addition  of  lime 
or  incomplete  boiling  some  of  the  arsenious  acid  may  be  present 
in  free  condition.  Haywood  examined  four  samples  with  the 
following  results: 

Per  cent 

Moisture 1 . 87-4 .07 

Sand  2.46-3-55 

Arsenious  acid,  total 6.40-17.31 

Arsenic  acid,  total 26.50-35.62 

Arsenious  acid,  soluble  in  cold  water. . .    1 .44-13.49 

Arsenic  acid,  soluble  in  cold  water 7.12-19.56 

Lime 23.59-25.09 

Water  decomposes  both  calcium  arsenate  and  calcium  arsenite 
to  some  extent  and  consequently  a  solubility  determination  with 
water  does  not  show  how  much  arsenious  acid  was  actually  free. 
These  soluble  arsenic  salts  are  probably  less  objectionable  than 
free  arsenious  acid,  although  it  is  recognized  that  London  purple 
is  more  injurious  to  foliage  than  is  Paris  green  and  common 
arsenic  (arsenious  oxide)  is  more  harmful  than  either.  This  con- 
dition may  be  corrected  by  adding  lime  to  the  London  purple 
when  suspending  it  in  water  for  application  to  foliage.  Since 
it  is  subject  to  considerable  variation  in  composition  this  insec- 
ticide should  be  bought  on  guarantee  of  purity. 

Calcium  arsenite  was  proposed  by  Kilgore  as  an  insecticide, 
following  his  observations  with  Paris  green.  This  can  be  made 
by  boiling  one  pound  of  arsenious  oxide  and  two  pounds  of  lime 
in  water  and  diluting  for  use.  Since  this  compound  has  been 
shown  to  form  about  75  per  cent  of  London  purple,  it  is  probably 
more  economical  to  use  the  latter  insecticide. 

Arsenite  of  soda  is  prepared  by  boiling  arsenious  oxide  with 
four  times  its  weight  of  sodium  carbonate.  The  injurious  effects 
of  this  compound  upon  potato  foliage  have  been  referred  to. 
Similar  results  were  produced  in  trials  of  sodium  arsenate  against 
the  gypsy  moth  in  Massachusetts. 


300  Agricultural  Chemistry. 

"Dips"  which  have  proved  very  efficient  in  destroying  sheep 
ticks  have  given  sodium  arsenite  recognition  as  a  valuable  in- 
secticide. The  following  formula  has  been  used  with  success : 

Arsenite  of  soda 5  pounds 

Soft  soap 5  pounds 

Aloes 12  ounces 

Water 100  gallons 

The  soap  is  said  to  increase  the  retention  of  the  dip  on  the 
fleece  and  aloes  renders  it  distasteful  to  the  animal  and  prevents 
poisoning.  Sodium  ar 'senate  has  been  used  against  locusts  by 
adding  it  to  sugared  water  and  spraying  the  grass  in  the  infested 
region. 

Lead  arsenate  was  recommended  as  an  insecticide  in  1892  and 
was  first  used  against  tent  caterpillars.  It  is  prepared  by  adding 
lead  acetate  to  sodium  arsenate  in  water.  These  substances  dis- 
solve readily  in  the  cold  and  react  to  form  sodium  acetate  and 
lead  arsenate.  the  latter  remaining  suspended  as  a  fine  white 
powder.  This  insecticide  should  be  handled  in  the  form  of  a 
paste,  for  once  dried  it  is  suspended  with  difficulty.  Recent  ex- 
periments show  that  lead  nitrate  is  to  be  preferred  to  the  acetate 
in  making  the  arsenate  because  the  product  remains  in  suspension 
better  and  contains  more  lead-hydrogen- arsenate,  carrying  a 
higher  percentage  of  arsenic  than  is  the  case  with  preparations 
from  the  acetate.  This  is  apparently  the  most  insoluble  of  all 
the  arsenical  insecticides  and  least  likely  to  scorch  the  foliage. 
Headden  has  shown,  however,  that  care  should  be  taken  to  use 
pure  water  in  the  preparation  of  even  this  spraying  mixture. 
Solutions  of  0.1  per  cent  sodium  sulphate  or  0.05  per  cent  com- 
mon salt  dissolve  considerable  amounts  of  arsenic  from  lead  ar- 
senate. Practical  spraying  tests  with  lead  arsenate  in  distilled 
water  showed  that  sodium  carbonate  or  sodium  chloride  at  the 
rate  of  10  grains  per  gallon  in  the  spray  fluid  produced  severe 
injury  and  40  grains  of  the  latter  salt  per  gallon  injured  about 
50  per  cent  of  the  foliage.  Salt  waters  and  alkali  surface  waters 
must  therefore  be  avoided. 


Insecticides  and  Delated  Substances.  301 

Haywood  gives  the  following  directions  for  preparing  lead 
arsenate ;  for  each  pound  of  lead  arsenate  to  be  made,  use — 

Ounces 

Formula  A.     Sodium  arsenate  (65  per  cent) 8 

Lead  acetate  (sugar  of  lead) 22 

Formula  H.     Sodium  arsenate  (65  per  cent) 8 

Lead  nitrate 18 

Dissolve  each  salt  separately  in  1  to  2  gallons  of  water,  using 
wooden  vessels.  When  dissolved,  pour  the  lead  solution  into  the 
sodium  arsenate,  stirring  thoroughly  until  the  mixture  just  turns 
a  potassium-iodide  test  paper  to  a  bright  yellow.  The  lead  salt 
is  then  in  slight  excess.  A  large  excess  should  be  avoided.  Al- 
low the  lead  arsenate  to  settle,  and  pour  off  the  liquid.  These 
chemicals  are  extremely  poisonous  and  should  be  plainly  labeled 
and  handled  with  care. 

Pink  arsenoid  is  a  commercial  preparation  made  by  adding 
lead  acetate  to  sodium  arsenite  and  coloring  the  insoluble  product 
with  a  dye.  It  is  composed  chiefly  of  lead  arsenite,  only  a  small 
proportion  of  the  arsenic  being  soluble,  and  has  given  satisfac- 
tory results. 

White  arsenoid  was  the  product  of  an  attempt  to  put  barium 
arsenite  upon  the  market  as  an  insecticide.  Contrary  to  expec- 
tation, all  the  arsenious  oxide  of  this  preparation  was  found  to 
be  soluble  in  cold  water.  It  gave  poor  results  and  was  short- 
lived. 

White  arsenic,  or  the  simple  arsenious  oxide,  has  been  used  as 
a  constituent  of  "dips"  and  various  insect  and  animal  poisons. 
It  is  volatile  at  a  comparatively  low  heat  and  mixed  with  sulphur, 
it  has  been  successfully  used  against  ants  by  forcing  the  vapors 
into  the  nest. 

Arsenical  poisoning  may  occur  in  the  case  of  trees  heavily 
sprayed  with  arsenical  insecticides.  Headden  found  arsenic  in 
diseased  fruit  trees  and  this  condition  was  correlated  with  an 
accumulation  of  arsenic  in  the  soil  in  compounds  from  which  it 
was  rendered  gradually  soluble  by  the  salts  of  the  soil  solution. 


;J02  Agricultural  Chemistry. 

Paige  found,  in  connection  with  reported  poisonings  associated 
with  combating  the  gypsy  moth,  that  the  amount  of  lead  arsenate 
consumed  hy  herbivora  with  the  grass  from  beneath  sprayed 
trees  might  lead  to  serious  results.  These  findings  emphasize  the 
need  of  care  in  the  use  of  poisonous  spraying  mixtures. 

Hellebore,  from  the  root  of  the  pokeroot  plant,  and  Pyrethrum 
or  insect  powder,  from  the  flower  heads  of  certain  plants,  have 
poisonous  insecticidal  properties  attributed  to  alkaloids.  Both 
deteriorate  with  age. 

Purity  and  efficiency  of  insecticides  can  only  be  insured  by 
purchasing  them  under  guarantee  or  under  recommendations 
from  reliable  authorities,  such  as  the  state  experiment  stations, 
or  by  the  purchase  of  simple  constituents  to  be  combined  by  the 
purchaser. 

Contact  poisons  may  act  by  their  caustic  properties  and  by 
absorption  from  the  surface  of  the  insect,  or  by  closing  the  tra- 
eheae  or  breathing  tubes.  These  will  now  receive  our  consid- 
eration. 

Lime-sulphur  wash  is  typical  of  the  former  class  of  insecti- 
cides. It  was  used  in  California  as  a  sheep  dip,  where  it  was 
Mist  applied  also  to  the  San  Jose  scale  in  1886.  The  wash  was 
prepared  by  boiling  sulphur  and  slaked  lime  in  equal  parts, 
which  produced  first  a  simple  sulphide  of  lime  (CaS)  of  a  white 
eolor.  Prolonged  boiling  causes  the  color  of  the  wash  to  pass 
through  shades  of  yellow  to  a  deep  orange  color  with  the  forma- 
tion of  poly-sulphides  of  lime  carrying  increasing  proportions  of 
sulphur.  The  chemistry  of  lime-sulphur  wash  has  been  inves- 
tigated at  the  New  York  Experiment  Station.  The  chief  com- 
pounds were  found  to  be  calcium  penta-sulphide  (CaS5),  calcium 
tetra-sulphide  (CaS4)  and  calcium  thiosulphate  (CaS2O3).  Boil- 
ing converts  the  last-named  compound  into  calcium  sulphite  and 
free  sulphur,  and  the  calcium  sulphite  then  oxidizes  by  exposure 
to  the  air  into  calcium  sulphate. 

The  specific  gravity  of  the  wash  and  the  amount  of  calcium 
and  sulphur  in  solution  increased  with  tli<>  amount  of  lime  used. 


Insecticides  and  Related  Substances.  303 

The  higher  amounts  of  lime  produced  more  calcium  tetra-sul- 
phide,  while  with  the  smaller  amounts,  the  mixture  was  more 
nearly  penta-sulphide.  The  largest  amount  of  soluble  sulphides 
was  formed  by  boiling  about  one  hour,  especially  when  the 
largest  amount  of  lime  was  used.  The  amount  of  sediment  in- 
creased with  increased  boiling,  due  to  the  formation  of  calcium 
sulphite.  It  was  found  that  the  addition  of  extra  lime  to  the 
diluted  lime-sulphur  solution  might  seriously  decrease  its  in- 
secticidal  value  as  a  result  of  the  decomposition  of  the  higher 
sulphides  of  calcium  with  formation  of  free  sulphur.  Where 
pure  lime  was  used,  the  sediment,  found  to  consist  of  calcium  sul- 
phite, free  sulphur  and  hydroxide  and  carbonate  of  lime,  formed 
suitable  material  to  add  in  the  making  of  a  new  wash.  It  was  also 
found  that  magnesium  oxide  when  present  in  the  lime,  as  in 
dolomitic  limestone,  tended  to  decompose  the  sulphides  of  cal- 
cium with  evolution  of  hydrogen  sulphide.  The  importance  of 
pure  lime  for  this  insecticide  is  thus  emphasized.  An  examina- 
tion of  commercial  lime-sulphur  preparations  revealed  great 
variations  in  composition.  Since  field  experiments  have  demon- 
strated that  this  insecticide  derives  its  chief  value  from  the 
soluble  lime-sulphur  compounds,  commercial  preparations  should 
be  bought  on  the  basis  of  the  strength  and  composition  of  their 
supernatant  liquid. 

Stewart  states  that  the  problem  of  making  concentrated  lime- 
sulphur  solutions  is  essentially  one  of  preventing  crystallization 
and  securing  a  storable  product  of  high  density.  He  finds  that 
the  formation  of  crystals  is  largely  due  to  an  excess  of  lime  and 
exposure  to  the  air  when  cold.  Exposure  to  the  air  may  be 
avoided  by  covering  the  surface  of  the  wash  with  oil.  Arsenite 
of  lime,  as  a  supplementary  insecticide,  has  been  found  to  pro- 
duce least  decomposition  of  the  sulphur  compounds  of  this  wash. 

liny  wood  found  that  a  one  hour  period  of  boiling  dissolved 
practically  all  the  sulphur  used  for  this  wash.  The  addition  of 
rommon  salt  was  found  to  have  no  effect  so  far  as  the  sulphur 
<-t impounds  of  the  wash  were  concerned. 


304:  Agricultural  Chemistry. 

On  theoretical  grounds,  Haywood  recommends  the  following 
formula  for  preparing,  at  minimum  cost,  a  wash  with  the  max- 
imum amount  of  sulphur  in  solution  and  a  moderate  excess  of 
lime: 

Lime 20-22^  pounds 

Sulphur 20  pounds 

Water 50  gallons 

The  mixture  is  best  when  boiled  by  passing  steam  through  it. 
Moderate  slaking  of  the  lime  was  found  to  have  no  influence,  but 
a  comparison  of  flowers  of  sulphur  and  crystallized  sulphur 
showed  that  the  crystalline  form,  even  when  finely  ground,  re- 
quired much  longer  boiling  for  maximum  solution  and  gave  a 
product  of  variable  composition,  apparently  dependent  on  the 
size  of  the  particles. 

To  determine  what  changes  take  place  after  the  wash  is  ap- 
plied to  trees,  measured  quantities  of  the  clear  liquid  were  ab- 
sorbed on  filter  papers  and  dried  in  the  open  air  exposed  to  sun- 
light. Analyses  at  successive  stages  showed  the  gradual  oxida- 
tion of  calcium  penta-sulphide  into  calcium  thiosulphate,  calcium 
sulphite  and  finally  calcium  sulphate,  with  deposition  of  free 
sulphur.  Wetting  the  paper  daily  to  simulate  the  daily  wetting 
of  branches  by  dew  greatly  increased  the  rapidity  of  the  process. 
Indications  were,  that  after  four  to  six  months  only  free  sulphur 
and  calcium  sulphate  would  be  left.  Haywood  believes  that  the 
excess  of  caustic  lime  loosens  the  scale  insects  from  the  tree,  and 
that  the  active  agents  in  killing  are  sulphur  in  finely  divided 
form,  thiosulphate,  for  a  time,  and  sulphite,  which  is  gradually 
formed  by  the  slow  oxidations. 

Self  boiled  washes,  in  which  the  heat  for  solution  is  produced 
by  the  chemical  reaction  incident  to  slaking  the  lime,  are  un- 
satisfactory, even  when  a  maximum  amount  of  heat  is  so  gen- 
erated. 

Lime,  sulphur,  salt,  soda-wash,  in  which  caustic  soda  is  used 
in  addition  to  lime,  has  nearly  the  same  composition  and  action 
as  the  simpler  wash  already  described.  It  is  less  effective,  how- 


Insecticides  and  Related  Substances.  305 

ever,  because  it  decomposes  more  slowly  and  the  sodium  sulphite 
formed  is  more  subject  to  loss  by  washing  than  is  calcium 
sulphite. 

Kerosene  has  been  used  as  a  contact  insecticide  against  scale 
insects.  It  is  applied  as  a  spray  to  the  dormant  trees,  but  is 
frequently  injurious.  Applied  to  stagnant  pools,  it  effectually 
suffocates  the  emerging  pupae  of  mosquitoes;  and  in  the  "hop- 
per-dozer" it  destroys  grasshoppers  which  are  trapped  in  it,  by 
forming  an  oil  film  over  the  tracheae. 

Kerowater  sprays  were  the  result  of  attempts  to  dilute  kero- 
sene before  applying  it  to  trees.  Kerosene  is  not  miscible  with 
water  but  by  forcibly  mixing  these  liquids  at  the  nozzle  of  the 
spray  pump  the  kerosene  was  temporarily  diluted. 

Kerosene  emulsions  are  comparatively  permanent  suspensions 
made  by  mixing  kerosene  oil  with  soap  solutions.  They  are  not 
true  solutions,  for  the  oil  can  be  observed  under  a  microscope  as 
droplets  suspended  in  the  soap  solution.  Well  made  emulsions 
persist  for  several  hours,  and  even  for  days,  and  facilitate  an 
even  distribution  of  the  kerosene.  Crude  petroleum  oils,  which 
are  closely  related  to  kerosene  but  less  volatile  than  the  latter* 
have  taken  its  place  to  a  great  extent  because  of  the  greater 
efficiency  and  safety  attendant  upon  their  use. 

Miscible  oils  are  preparations  of  this  nature.  They  are  based 
on  a  standard  soap  solution  with  which  various  proportions  of 
different  oils  are  emulsified.  Crude  oil,  a  mixture  of  petroleum 
oils  heavier  than  kerosene;  paraffin  oil,  a  lubricating  oil  from 
petroleum ;  and  resin  oil,  from  the  distillation  of  resin,  are  used. 
The  crude  oils  are  efficient  in  6  2/3  per  cent  strengths,  whereas 
kerosene  is  inefficient  below  20  per  cent  strength. 

Penny  gives  the  following  formula  for  a  standard  miscible  oil : 

The  "Soap  Solution." 

Menhaden  oil 10  gallons 

Carbolic  acid 8     " 

Caustic  potash 15     " 

Heat  to  290°  or  300°  F.,  then  add  kerosene 2     " 

Water 2     " 


306  Agricultural  Chemistry. 

From  the  above  soap  solution,  the  miscible  oil  is  prepared  ac- 
cording to  the  following  formula : 

Soap  solution 3%  gallons 

Paraffine  oil 40 

Rosin  oil r> 

Water,  as  required  by  test. 

In  the  process  of  making  the  soap  solution  the  kerosene  should 
be  added  while  the  soap  is  hot.  The  heavier  oils  should  be  stirred 
into  the  soap  solution  at  moderate  temperatures.  Freezing  tem- 
peratures should  be  avoided.  The  amount  of  water  to  be  added 
is  a  matter  of  experiment  but  it  should  be  used  in  quantity  suffi- 
cient to  produce  an  emulsion  of  creamy  consistency.  One  gallon 
of  the  soap  solution  or  cmulsifier  will  make  8  to  14  gallons  of 
miscible  oil  and  these  8  to  14  gallons  will  make  from  100  to  210 
gallons  of  spray  material,  according  to  dilution. 

Resin  soaps,  efficient  against  orange  scale  insects,  are  prepared 
by  boiling  resin  with  carbonate  of  soda  and  diluting  the  solid 
product  with  water. 

Fish  oil  soap  and  whale  oil  soap,  prepared  by  boiling  the  oils 
in  potash  lye  and  diluting  with  water,  are  effective  against  plant 
and  animal  lice,  but  the  commercial  preparations  are  subject  to 
great  variations  in  composition. 

Tobacco  decoction  depends  for  its  value  upon  the  poisonous 
properties  of  nicotine.  This  alkaloid  is  soluble  in  water,  and 
hot  water  extractions  of  the  stalk  and  waste  of  tobacco  are  used 
as  an  insecticide. 

Gaseous  insecticides  are  used  against  insects  particularly  dif- 
ficult to  attack.  Hydrocyanic  acid  gas  is  by  far  the  most  effec- 
tive substance  in  this  class.  It  is  produced  from : — 

Potassium  cyanide,  pure 1  ounce 

Sulphuric  acid,  commercial 2      " 

Water 4      " 

This  is  the  quantity  recommended  for  each  100  cubic  feet  of 
space.  The  cyanide  should  be  added  last,  having  the  mixture  in 


Insecticides  and  Related  Substances.  307 

an  earthen- ware  vessel.  Potassium  sulphate  is  formed  and  the 
poisonous  hydrocyanic  acid  is  rapidly  liberated  as  an  invisible 
gas.  This  is  an  extremely  powerful  poison,  a  single  breath  being 
fatal,  and  by  no  means  should  it  be  inhaled  by  the  operator. 
To  retain  the  gas  and  secure  efficient  action,  it  should  be  applied 
in  tightly  closed  rooms  or  buildings,  or  in  tents  specifically  pro- 
vided for  the  purpose,  allowing  it  to  act  for  an  hour  or  more. 
The  enclosure  should  then  be  opened  from  the  outside  and  thor- 
oughly aired  before  being  entered,  and  the  strongly  acid  residue 
from  the  reaction  should  be  carefully  disposed  of. 

Carbon  bisulphide  is  a  colorless,  volatile  liquid  formed  by  pass- 
ing sulphur  vapors  over  red  hot  charcoal.  The  gas  evolved  from 
the  liquid  is  heavier  than  air,  inflammable  and  fatal  to  insects 
breathing  it.  Its  chief  use  is  for  the  destruction  of  weevils  in 
grain.  One  teaspoonful  for  each  cubic  foot  of  space  should  be 
placed  in  a  shallow  dish  at  the  surface  of  the  grain,  and  one  hour 
allowed  for  the  evaporation  of  each  teaspoonful  used.  The  heavy 
vapors  sink  through  the  grain  to  the  bottom  of  the  bin,  where 
they  may  be  released  by  boring  holes  through  the  wall.  Ants, 
moles,  prairie  dogs  and  similar  pests  are  exterminated  by  placing 
cotton  saturated  with  carbon  bisulphide  in  the  heaps  or  runs  and 
covering  tightly.  Carbon  bisulphide  should  never  be  brought 
near  flames. 

Fungicides  are  materials  utilized  for  the  destruction  of  para- 
sitic plants.  Hyposulphite  of  soda,  lime-sulphur  and  sulphur 
alone  were  used  in  this  capacity  as  early  as  1885  against  apple 
scab  and  leaf  blight. 

Bordeaux  mixture  has  been  the  premier  fungicide  since  1883, 
when  Millardet  used  it  against  the  downy  mildew  of  the  grape. 
It  was  accidentally  discovered  by  observing  the  flourishing  con- 
dition of  vines  to  which  lime  and  copper  salts  had  been  applied 
to  prevent  the  theft  of  grapes  in  the  province  of  Bordeaux, 
France.  Several  formulae  have  been  superseded  generally  by 


308 


Agricultural  Chemistry. 


the  so-called  "normal"  formula,  or  1.6  per  cent  Bordeaux,  which 
consists  of: 

Copper  sulphate 6  Ibs. 

Quick  lime 4  Ibs. 

Water 50  gallons 

The  lime  should  be  slightly  in  excess.  This  may  be  accom- 
plished by  weighing  the  pure  salts  for  the  mixture,  or  by  testing 
the  product. 


Note  the  beneficial  results  from  the  control  of  potato  diseases  by  Bor- 
deaux mixture. 

The  litmus  test  depends  upon  the  fact  that  so  long  as  copper 
sulphate  is  in  excess  blue  litmus  will  be  turned  red  when  moist- 
ened with  the  Bordeaux  mixture.  Enough  lime  should  be  pres- 
ent so  that  red  litmus  is  turned  blue. 

The  ferro-cyanide  test  may  be  used  also  for  this  purpose.  A 
teaspoonful  of  the  clear  liquid,  obtained  by  straining  if  necessary, 
should  be  added  to  a  few  drops  of  potassium-ferrocyanide  solu- 


Insecticides  and  Related  Substances.  309 

tion  in  a  white  porcelain  dish.  A  reddish  brown  precipitate  or 
color  indicates  the  presence  of  soluble  copper  salts,  and  lime 
should  be  added  to  the  mixture  until  this  no  longer  appears. 

The  fungicidal  properties  of  Bordeaux  mixture  are  chiefly  due 
to  the  insoluble  compounds  formed  and  it  is  important  to  keep 
these  thoroughly  in  suspension.  To  facilitate  this,  the  copper 
sulphate  and  lime  should  be  dissolved  separately,  each  in  one-half 
the  water,  and  when  the  lime  is  cool,  they  should  be  poured  to- 
gether with  constant  stirring.  In  this  way,  the  dilute  solutions 
react  to  form  a  fine  suspension  which  will  not  settle  for  several 
hours.  The  chemistry  of  Bordeaux  mixture  has  not  been  thor- 
oughly investigated.  According  to  Lodeman,  when  the  copper- 
sulphate  is  just  neutralized,  most  of  the  copper  is  probably  pre- 
cipitated as  a  hydrate ;  but  excess  of  lime  added  to  a  concentrated 
"mixture"  forms  another  compound  which  may  be  a  basic  sul- 
phate of  copper  and  lime. 

Soda  Bordeaux,  made  with  caustic  soda  in  place  of  lime  in 
the  regular  formula,  has  given  satisfactory  results. 

Copper  ammonium  sulphate,  a  clear  blue  solution  formed 
from  copper  sulphate  and  ammonia,  also  called  "eau  celeste," 
has  been  applied  as  a  fungicide,  but  its  caustic  action  renders 
it  unsafe.  Copper  carbonate  dissolved  in  ammonia,  however,  has 
given  good  results.  It  should  be  freshly  prepared,  as  the  am- 
monia may  volatilize  on  standing,  causing  the  copper  to  fall  out 
of  solution. 

Copper  sulphate  has  been  applied  to  dormant  trees  and  green  - 
house  plants  as  a  dilute  solution,  but  it  possesses  a  strongly  acid 
reaction  and  should  be  used  with  care.  Smut  on  grains  is  de- 
stroyed by  this  fungicide.  A  one  to  two  hour  immersion  of  oats 
in  a  0.5  to  1.0  per  cent  solution  may  be  safely  practiced,  but 
stronger  applications  retard  germination. 

Potassium  sulphide  is  used  against  mildews  at  the  rate  of 
one-half  ounce  to  one  gallon  of  water.  Strong  solutions  are 
destructive  to  plants.  Potash  lye  and  formaldehyde-glycerine 


310  Agricultural  Chemistry. 

mixture,  properly  diluted,  have  proved  valuable  fungicides  under 
certain  conditions. 

Formalin  or  formaldehyde,  is  a  most  efficient  agent  for  destroy- 
ing smut  spores  on  grain.  The  seed  should  be  immersed  for  ten 
minutes  in  a  solution  of  1  pint  of  "40  per  cent"  formalin  to 
20  gallons  of  water.  Stronger  solutions  have  been  found  in- 
jurious to  the  germinating  power  of  barley.  The  seed  should  be 
spread  and  finally  mixed  so  as  to  dry  with  not  more  than  two 
to  three  hours  contact  with  the  formalin. 

Disinfectants  are  substances  which  accomplish  the  total  de- 
struction of  the  germs  of  infectious  diseases.  They  may  also  act 
as  deodorants  or  destroyers  of  foul  odors. 

Antiseptics  prevent  decomposition  or  putrefaction  by  arrest- 
ing the  development  of  germs,  but  do  not  necessarily  destroy 
them.  Disinfectants  in  weak  solutions  may  act  as  antiseptics. 
Refrigeration,  common  salt  and  sugar,  all  of  which  are  largely 
used  in  preserving  fruits,  meats,  etc.,  are  good  examples  of  anti- 
septics. 

Formaldehyde  is  perhaps  the  most  commonly  used  chemical 
disinfectant.  It  is  a  product  of  the  oxidation  of  wood  alcohol 
and  is  put  upon  the  market  in  a  38  to  40  per  cent  solution  in 
water.  A  five  per  cent  solution  made  from  this  should  be  mixed 
with  any  solid  matter  to  be  disinfected.  Gaseous  formalde- 
hyde is  used  for  disinfecting  inclosed"  space  and  porous  solid 
matter  in  bulk.  The  gas  should  be  delivered  into  a  tightly  closed 
compartment  in  one  of  the  following  ways:  Formalin  may  be 
heated  under  pressure  or  in  a  simple  retort  and  the  gas  piped 
into  the  space;  formalin  may  be  sprayed  upon  sheets  or  other 
extensive  surfaces  in  the  space  to  be  disinfected  and  the  gas 
liberated  by  simple  evaporation;  six  parts  of  formalin  may  be 
poured  upon  five  parts  by  weight  of  chemically  pure  potassium 
permanganate.  In  the  last  case,  heat  is  generated  by  chemical 
reaction  and  50  per  cent  of  the  formaldehyde  is  liberated  as  a 
gas.  Ten  ounces  of  formalin  are  necessary  for  each  1000  cubic 


Insecticides  and  Related  Substances.  311 

feet  of  space  in  the  first  two  cases  and  twice  as  much  must  be  used 
in  the  permanganate  method.  This  disinfectant  also  acts  as  a 
deodorant. 

Paraform  is  a  condensed  form  of  formaldehyde  put  up  as  a 
powder  or  as  pastils.  Two  ounces  of  paraform  liberate  gas  suf- 
ficient to  disinfect  1000  cubic  feet  of  space. 

Mercuric  chloride  or  corrosive  sublimate  is  a  poisonous,  white, 
crystalline  salt.  It  is  usually  put  up  in  tablet  form  with  am- 
monium chloride  to  facilitate  dissolving  in  water.  Strengths  of 
1  to  500  to  1  to  1000  are  used,  the  greater  strength  being  neces- 
sary to  destroy  bacterial  spores.  This  is  a  powerful  stomachic 
poisoning  and  must  be  handled  with  care.  It  forms  insoluble 
compounds  with  proteins  and  hence  raw  eggs  and  milk  are  given 
as  antidotes.  On  account  of  its  chemical  affinity  for  proteins, 
unless  liberally  used  it  has  little  disinfecting  power  when  applied 
to  excreta,  blood  and  similar  protein  containing  materials.  Solu- 
tions of  this  salt  should  be  used  only  in  glass  or  earthern  ware, 
as  it  reacts  with  tin  and  other  common  metals. 

Chloride  of  lime  (bleaching  powder)  is  both  a  disinfectant  and 
deodorizer.  It  is  prepared  by  passing  chlorine  gas  over  slaked 
lime.  The  compound  decomposes  rapidly  on  exposure  to  the 
air  and  hence  is  put  up  in  hermetically  sealed  containers  and  is 
reliable  only  when  freshly  removed  from  these. 

Carbolic  acid  is  a  derivative  of  benzene,  a  hydrocarbon  which 
forms  the  basis  of  the  coal  tar  dyes.  At  ordinary  temperatures 
it  has  the  crystalline  form  of  long,  white  needles.  One  part  of 
water  to  9  parts  of  the  crystals  produces  a  liquid,  in  which  form 
it  is  commonly  dispensed.  By  dissolving  in  warm  water  a  solu- 
tion of  slightly  over  6  per  cent  carbolic  acid  can  be  made.  This 
is  used  as  a  spray  and  wash.  Crude  carbolic  acid  is  a  crude  prep- 
aration from  coal  tar  distillation,  the  latter  substance  being  the 
liquid  by-product  in  the  production  of  gas  and  coke  from  coal. 
This  disinfectant  is  a  mixture  of  various  coal  tar  oils  and  so- 
called  "cresylic  acid/'  and  contains  little  or  no  true  carbolic 
acid.  The  disinfecting  power  is  due  to  cresols  of  the  "cresylic 


312  Agricultural  Chemistry. 

acid,"  bodies  related  to  carbolic  acid.  Therefore  the  "cresylic 
acid"  content  of  the  crude  material  should  be  known  and  from 
this  a  2  per  cent  solution  of  the  constituent  made.  The  undis- 
solved  cresols  that  are  present  necessitate  a  thorough  mixing 
while  spraying  in  order  to  facilitate  an  even  distribution  of  the 
material 

Cresol  (trikresol)  is  supplied  to  the  trade  from  the  coal  tar 
industry  in  varying  degrees  of  purity.  It  contains  bodies  of 
the  same  general  composition,  but  which  are  superior  to  car- 
bolic acid  as  disinfectants.  Grades  containing  less  than  90  per 
cent  of  "cresylic  acid"  (cresols)  are  undesirable  because  of  the 
suppression  of  solubility  of  the  cresols  by  the  oils  usually  present 
as  impurities.  A  2  per  cent  cresol  solution  is  considered  superior 
to  a  5  per  cent  solution  of  carbolic  acid. 

Liquid  carbolic  acid  is  a  mixture  of  cresols,  usually  90  to 
98  per  cent  pure,  which  should  be  bought  on  guaranteed  content 
of  "cresylic  acid."  Compoutid  solution  of  cresol  is  a  mixture 
of  equal  parts  of  cresol  and  linseed-oil-potash  soap.  It  is  ap- 
plied like  cresol  with  the  added  advantage  of  greater  solubility 
in  water. 

These  coal  tar  compounds  are  the  basis  also  of  a  number  of 
commercial,  soluble  disinfectants  and  dips,  such  as  creolin,  lysol. 
solveol,  Car-Sul  dip,  carboleum,  cresol,  disinfectall,  germol,  and 
zenoleum.  Fly  removers,  applied  to  animals  for  protection 
against  flies,  have  been  prepared  from  these  substances.  Light 
coal  tar  oil  for  this  purpose  has  given  the  most  satisfaction  as 
to  persistence  and  freedom  from  gumming  on  the  animal's  coat. 

Creosote  preparations  for  antiseptic  treatment  of  timbers 
against  bacteria  and  fungi  are  the  heavier  fractions  of  coal  tar 
oil  and  carry  carbolic  acid,  the  cresols,  naphthalene,  (also  used 
in  moth  balls) ,  anthracene,  and  similar  high-boiling  hydrocarbons 
and  carbolic-acid-like  bodies. 

Deodorants  include  some  of  the  above  materials,  such  as 
chloride  of  lime,  which  destroy  the  causal  substance  through 
chemical  action.  Other  substances  merely  cover  up  the  offensive 


Insecticides  and  Related  Substances.  313 

odor  by  the  odor  they  themselves  produce  Charcoal  is  a 
deodorant  by  virtue  of  its  great  absorptive  capacity  for  gases. 
It  acts  by  mechanical  absorption  of  offensive  gases  into  its  pores. 
Incidental  materials.  Use  is  often  made  of  arsenite  of  soda, 
common  salt,  carbolic  acid,  sulphuric  acid  and  other  compounds, 
as  weed  destroyers.  Iron  sulphate  solution,  prepared  by  dissolv- 
ing 100  pounds  of  the  granulated  salt  in  50  gallons  of  water  for 
each  acre  of  land  has  been  successfully  used  in  eradicating  wild 
mustard.  Untoward  effects  of  these  substances  on  the  soil  can 
be  corrected  in  many  cases  by  applications  of  lime.  Copper  sul- 
phate applied  to  reservoirs  at  the  rate  of  one  part  of  salt  to  from 
one  million  to  ten  million  parts  of  water  has  been  extensively 
used  in  destroying  algae  growth. 


APPENDIX 


COMPOSITION  OF  SOILS. 

Snyder  gives  the  following  average  composition  of  200  fertile 
soils;  analysis  was  made  by  strong  hydrochloric  acid. 

Insoluble  matter , 79.95  Per  cent. 

Potash 0.29  "       " 

Soda 0.25  «       " 

Lime 2.16  "       " 

Magnesia 0.55 

Iron  oxide 2.68  "       " 

Alumina 5.20  " 

Phosphor  acid 0 . 24 

Sulphur  trioxide 0.03  "       " 

Carbone     dioxide 1.12    "      " 

Volatile  matter 7.00  " 

99.47 
Volatile  matter  containing: 

Humus 3.35  "       " 

Nitrogen , 29  "       " 


316 


Agricultural  Chemistry. 

Fertilizing  Constituents  in  One  Ton  of  Material. 


Feed 


Nitrogen 
Ibs. 


Phosphoric 
acid,  Ibs. 


Potash 
Ibs. 


Dry  matter 
Ibs. 


Concentrates 

Corn 36.4 

Corn  bran 32.6 

Hominy  chops 32.6 

Gluten  feed 76.8 

Wheat 47.2 

Wheat  middlings 52.6 

Rye 35.2 

Barley 30.2 

Malt  sprouts 71 .0 

Brewers'  grains  (dried) ."  72.4 

Oat  feed 34-4 

Cotton  seed  meal 13.5 

Peas 61.6 

Roughage 

Corn  stover 20.8 

Timothy  hay 25.2 

Red  clover  hay  (medium) 41.4 

Red  clover  hay  (mammoth). ...  44.6 

Crimson  clover  hay 41-0 

Alfalfa  hay ". 43.8 

Silage 

Corn 5.6 

Straw 

Oat 12.4 

Barley 26.2 

Roots  and  Tubers 

Potatoes 6.4 

Beet,  common 4.8 

Beet,  sugar 4.4 

Rutabaga 3.8 

Turnip 3.6 

Miscellaneous 

Cabbage  7.6 

Rape 9.0 


14.0 
24.2 
19.6 
8.2 
15.8 
19.0 
16.4 
15.8 
28.6 
20.6 
18.2 
57.6 
16.4 

5.8 
10.6 

7.6 
11.0 

8.0 
10.2 

2.2 

4.0 
6.0 

2.4 
1.8 
2.0 
2.4 
2.0 

2.2 
3.0 


8.0 
13.6 

9.8 

0.6 
10.0 
12.6 
10.8 

9.6 
32.6 

1.8 
10.6 
17.4 
19.8 

28.0 
18.0 
44.0 
24.4 
26.2 
33.6 

7.4 

24.8 
41.8 

9.2 
8.8 
9.6 
9.8 

7.8 

8.6 
7.2 


1,764 
1,818 

1,844 
,732 
,748 
,714 
,714 
,760 
,810 
,734 
,823 
,720 

1,816 
1,726 
1,684 
1,7-2 
1,672 
1,850 

441 

1,710 
1,716 

500 
245 
360 
218 
184 

220 
290 


Appendix. 


sir 


COMPOSITION  OF  FERTILIZERS. 

Composition  of  fertilizer  materials  supplying  nitrogen. 


' 

Per  cent 
Nitrogen 

Per  cent 
Phosphoric 
acid 

Per  cent 
Potash 

Nitrate  of  soda.       

15  5-16 

Sulphate  of  ammonia  

19    -20  5 

Dried  blood  (high  grade)  

12    -14 

Concentrated  tankage  

11    -12  5 

1-2 

Tankage  (bone)  

5-6 

11  -  14 

Nitrogenous  guano.  .  .             

3-7 

9-19 

2-4 

Composition  of  fertilizing  materials  supplying  phosphoric  acid. 


Per  cent 
Phosphoric 
acid 

Per  cent 
Nitrogen 

S.  Carolina  rock  (ground)  (floats) 

25  -  30 

S.  Carolina  rock  (dissolved) 

12  -  16 

Florida  rock  

25  -  30 

Thomas  slag 

18-23 

Ground  bone  

20  -  25 

2.5  -  4.& 

Steamed  bone  

22  -  29 

1.5  -  2.5- 

Bone  black 

32  -  36 

Composition  of  fertilizer  materials  supplying  potash. 


Per  cent 
Potash 

Per  cent 
Nitrogen 

Per  cent 
Phosphoric 
acid 

Muriate  of  potash  (80-85  per  cent  pure)  
Sulphate  of  potash  (  high  grade)  
Sulphate  of  potash  (low  grade  )  
Kain  it 

50  -  53 
48  -  52 
28  -  30 
12      13 





Tobacco  stems 

3-8 

2-3 

3-5 

Wood  ashes  

*4  -     8 

1  -  2 

318 


Agricultural  Chemistry. 


COMPOSITION  OF  FEEDING  STUFFS. 
The  following  brief  table  gives  the  composition  of  some  typical 
feeding  materials    (taken    from   "The   Feeding   of   Animals," 
Jordan,  Appendix) : 


-u 

(H      C 

<X>   0) 

3° 

n 

+3 

-si 

<1    K 
& 

Crude  Protein 
per  cent 

&G 

s  I 
1* 

2  ft 

0 

Nitrogen-free 
extract 
per  cent 

Ether  extract 
per  cent 

FODDERS 
Corn  fodder  (green)         

79  3 

1  2 

1  8 

5  0 

*[•>.    9 

5 

(field  cured)  
Corn  silage                      .  . 

42.2 
79.1 

2.7 
1.4 

4.5 

1.7 

14.3 
6.0 

34.7 
11  0 

1.8 

8 

Timothy  (green)                     .... 

61  6 

2.1 

3  1 

11.8 

20  2 

1  2 

'•          hay  
Alfalfa  (green)          

13.2 

71.8 

4.4 

2.7 

5.9 

4.8 

29.0 

7  4 

45.0 
12  3 

2.5 

1  0 

"       h«y         ,  .  .  .       

8.4 

7.4 

14  3 

25  0 

42  7 

2  2 

Clover  hay  (red)  .       

15.3 

6.2 

12  3 

24  8 

38.1 

3  3 

ROOTS 
Turnips 

90.5 

8 

1  1 

1  2 

6  2 

2 

Rutabagas                

88.6 

1  2 

1  2 

1  3 

7  5 

2 

GRAINS 
Corn  

10.9 

1  5 

10  5 

2  1 

69  6 

5  4 

Barley  

10.9 

2  4 

12  4 

2  7 

69  8 

1.8 

Oats  

11. 

3 

11  8 

9  5 

59  7 

5 

Wheat  

10.5 

1  8 

11  9 

1  8 

71.9 

2  1 

MILL  PRODUCTS 
Corn  meal  

15. 

1   4 

9  2 

1  9 

68  7 

3  8 

Corn-and-cob  meal  

15.1 

1  5 

8  5 

6  6 

64  8 

3  5 

Wheat  flour  

12  4 

5 

10  8 

2 

75 

1.1 

Wheat  bran  

11  9 

5.8 

15  4 

9  0 

53  9 

4.0 

Gluten  feed  

7  8 

1  i 

24  0 

5  3 

51  2 

10  6 

Oat  feed  

7  7 

3  7 

16.0 

6  1 

59  4 

7  1 

Brewers'  grains  (dried).  . 

8  2 

3  6 

19  9 

n 

51  7 

5.6 

Linpeed  meal  (new  process)  
Malt  sprouts  

10.0 
5  0 

5.2 
6  4 

36.1 
27  6 

8.4 
10  9 

36.7 
47  1 

3.6 
3.0 

Appendix. 


319 


AVERAGE  COEFFICIENTS  OF  DIGESTIBILITY. 

A  brief  table  giving  the  coefficients  of  digestibility  of  important  feeding 
materials.     Taken  from  the  "  Feeding  of  Animals"  (Jordan). 

Digestion  by  Ruminants. 


„ 

a 

'£•* 

I 

Feed 

H 

££~cs  *, 

°a* 

II 
i* 

Q 

1| 

Nitrogen-i 
extract 
per  cen 

*§ 

0>   0 

!* 

w 

FODDERS. 
Corn  fodder  (green)  
(field  cured) 
Corn  silage.               .  .    . 

67.8 
68.2 
70  8 

69.8 
70.7 
73.6 

35.6 
30.6 
30.3 

59.7 
56.1 
56  0 

60.2 
65.8 
70.0 

73.7 
72.7 
76.1 

74.1 
73.9 

82  4 

Timothy  (green)  
"         hay  

63.5 
56  6 

65.6 
57  9 

32.2 

32.8 

48.1 
46  9 

55.6 
52  5 

65.7 
62.3 

53.1 
52  2 

Alfalfa  (green)  
"       hay  . 

67.0 

58.9 

64.0 
60.7 

39^5 

81.0 
72  0 

41.0 
46  0 

72.0 
69  2 

45.0 
51.0 

ROOTS. 
Turnips  

92.8 

96.1 

58.6 

89.7 

103  0 

96  5 

87  5 

Rutabagas  

87.2 

91.1 

31.2 

80.3 

74.2 

94.7 

84.2 

GRAINS. 
Corn  

89.4 

89.6 

67  9 

58  0 

94  6 

92.1 

Barley 

86  0 

70  0 

50  0 

92  0 

89  0 

Oat  

71.0 

78  0 

26.0 

77.0 

83.0 

MILL  PRODUCTS. 
Corn  meal  
Corn  and  cob  meal  
Wheat  bran  

89.4 
78.7 
62.3 

89.6 
79.8 
65.7 



67.9 
55.6 

77.8 

28.6 

94.6 

87.6 
69.4 

92.1 
84.1 
68.0 

Gluten  feed  

86.3 

87.3 

85.6 

78.0 

89.2 

84.4 

Oat  feed  

62.0 

65.3 

81.1 

42.6 

67.4 

89.0 

Brewers'  grains  (dried)  .  . 
Linseed  meal  (new  proc- 
ess)   

61.6 
79.2 

65.4 
81.8 

79.3 

85.2 

52.6 
80.4 

57.8 
86.1 

91.1 
96.6 

Malt  sprouts  .  . 

67.1 

67.2 

80.2 

32.9 

68.1 

104.6 

Timothy  (hay) 
Alfalfa  (hay).. 
Oat  (grain) . .  . 
Barley  "  ... 
Corn 


Digestion  by  Horses. 
43.5     44.1      34.0 

58.0 

69.0 

87.0 

89.0 

Digestion  by  Swine. 


21.2 
73.0 
79.0 
80.0 
75.6 


42.6 
40.0 
29.0 

46!6 


47.3 
70.0 
75.0 

87.0 
95.7 


Barley  

80  1 

80.3 

5.4 

81.4 

48.7 

86.6 

57.0 

Corn  (unground) 

89  7 

91  3 

89.9 

48  7 

93  9 

77.6 

Corn  (finely  ground) 

89.5 

91.2 

86.1 

29.4 

94.2 

81.7 

Corn  and  cob  meal 

75.6 

76.7 

75.7 

28.5 

83.6 

82.0 

Wheat  (unground)  .      .    .. 

72.0 

44.0 

70.0 

30.0 

74.0 

60.0 

Wheat  (cracked) 

82  0 

50  0 

80  0 

60.0 

83.0 

70.0 

"     bran  '. 
Linseed  meal  

65.8 

77.5 



'io.'o' 

75  1 

86.0 

33.0 
12.0 

65.5 
85.0 

71.8 
80.0 

320 


Agricultural  Chemistry. 


WOLFF'S  FEEDING  STANDARDS. 

Per  day  per  1000  Ibs.  live  weight. 


»       Kind  of  animal 

Total 
dry 
matter 

Digestible  organic  matter 

Nutritive 

Protein 

Carbo- 
ivdrates 

Fat 

ratio  1  : 

1  .     Oxen 
At  rest        

Lbs. 
18 
22 
25 

28 

30 
30 
26 

25 

29 

20 
23 
25 

30 

28 

20 
26 
22 

36 
32 
25 

Lbs. 
0.7 
1.4 
2.0 

2.8 

2.5 
3.0 

2.7 

1.6 
2.5 

1.2 
1.5 
2.9 

3.0 
3.5 

1.5 
2.5 
2.5 

4.5 
4.0 

2.7 

Lbs. 
8  0 
10.0 
11.5 
13.0 

15.0 
14.5 
15.0 

10.0 
13.0 

10.5 
12.0 
15.0 

15.0 
14.5 

9.5 
13.3 
15.5 

25.0 
24.0 
18.0 

Lbs. 
0.1 
0.3 
0.5 
0.8 

0.5 
0.7 
0.7 

0.3 
0.5 

0.2 
0.3 
0.5 

0.5 
0.0 

0.4 
0.8 
0.4 

0.7 
0.5 
0.4 

11.8 

7.7 
6.5 
5.3 

6.5 
5.4 

6.2 

6.7 
5.7 

9.1 
8.5 
5.6 

5.4 

4.5 

7.0 
6.0 
6.6 

5.9 
6.3 
7.0 

Light  work  

Moderate  work 

Severe  work  

•_'.     Tattening  bovines 
First  period 

Second  period 

Third  period 

3.     Milch  cows 
Daily  milk  yield  11  Ibs. 
Daily  milk  vield221bs. 
4.     Sheep 
Coarse  wool 

Fine  wool. 

Ewes,  suckling  lambs  
Fattening  sheep 
First  period  ... 

Second  period  

5.     Horses 
Light  work  

Heavy  work  

6.     Brood  sows 

7.     Fattening  swine 
First  period 

Second  period 

Third  period  

Appendix. 


321 


WOLFF'S  FEEDING  STANDARDS   (Continued). 


Kind  of  animal 
Age  in  months 

Live 
weight 
per 
head 

Total 
dry 
matter 

Digestible  organic  matter 

Nutritive 
ratio  1: 

Protein 

Carbo- 
hydrates 

Fat 

Growing  cattle 
DAIRY  BREEDS. 
2—3 

Lbs. 

150 
300 
500 
700 
900 

165 
330 
550 
750 
935 

60 
75 
85 
90 
100 

65 
85 
100 
120 
150 

45 
100 
120 
175 
260 

45 
110 
150 
200 
275 

Lbs. 

23 
24 
27 
26 
26 

23 
24 
25 
24 

24 

25 
25 
23 
22 
22 

26 
26 
24 
23 
22 

44 
35 
32 

28 
25 

44 
35 
33 
30 
26 

Lbs. 

4.0 
3.0 
2.0 

1.8 
1.5 

4.2 
3.5 
2.5 

2.0 

1.8 

3.4 
2.8 
2.1 
1.8 
1.5 

4.4 
3.5 
3.0 
2.2 
2.0 

7.6 
5.0 
3.7 

2.8 
2.1 

7.6 
5.0 
4.3 
3.6 
3.0 

Lbs. 

13.0 
12.8 
12.5 
12.5 
12.0 

13-0 
12.8 
13.2 
12.5 

12.0 

15.4 
13.8 
11.5 
11.2 
10.8 

15.5 
15.0 
14.3 
12.6 
12.0 

28.0 
23.1 
21.3 
18.7 
15.3 

28.0 
23.1 
22.3 
20.5 
18.3 

Lbs. 

2.0 
1.0 
0.5 
.0.4 
0.3 

2.0 
1.5 
0.7 
0.5 
0.4 

0.7 
0  6 
0.5 
0.4 
0.3 

0.9 
0.7 
0.5 
0.5 
0.4 

1.0 
0.8 
0.4 
0.3 
0.2 

1.0 
0.8 
0.6 
0.4 
0.3 

4.5 
5.1 

6.8X 
7.5 

8.5 

4.2 
4.7 
6.0 

6.8 

7.2 

5.0 
5.4 
6.0 

7.0 

7.7 

4.0 
4.8 
5.2 
6.3 
6.5 

4.0 
5.0 
6.0 

730 
7.5 

4.0 
5.0 
5.5 
6.0 
6.4 

3—6 

6—12 

12  —  18 

18—24 

BEEF  BREEDS. 
2—3 

3—6   .      .. 

6  —  12 

12—18  

18—24    .. 

Growing  sheep 
WOOL  BREEDS. 
4—6 

6—8  

8—11... 

11—15  

15—20  

MUTTON  BREEDS. 
4—6  

6—8  

8—11  

11—15  

15—20  

Growing  swine. 
BREEDING  STOCK. 
2—3 

3—5 

5—6 

6—8 

8—12.    . 

Growing  Fattening 
Animals. 
2—3  

3—5  

5—6  

6—8  

8-12  

322 


Agricultural  Chemistry. 


PRODUCTION  VALUES  PER  100  POUNDS. 

A  table  giving  the  productive  value  of  feeds  for  fattening  pur- 
poses.     Computed  according  to  Kellner. 


Feeding  Stuff 

Total 
Dry 
Matter 

Total 
Crude 
Fiber 

Digestible 

1      - 
1I§ 

!*! 

OH 

a 

1 
1 

if 

<*! 

2  . 

Green  Fodder  and  Silage: 
Alfalfa  

Lbs. 

28.2 
29.2 
20.7 
25.6 
28.9 
23.4 
38.4 

91.6 
84.7 
57.8 

59.5 
89.3 
92.3 
84.0 
88.7 
86.8 

90.8 
92.9 
90.4 

11.4 
9.1 
21.1 
9.5 

89.1 
89.1 
84.9 
89.0 
88.4 
89.5 

24.3 
91.8 
91.9 
91.8 

90.8 
90.1 
89.8 
88.2 
88.5 

Lbs. 
7.4 
8.1 
5.0 
5.8 
9.2 
11.6 
11.8 

25.0 
24.8 
14.3 
19.7 
20.1 
27.7 
27.2 
22.3 
29.6 

37.0 
38.9 
38.1 

1.3 
0  8 
0.6 
1  2 

2.7 
2.1 
6.6 
9.5 
1.7 
1.8 

3.8 
5.6 
6.4 
6.1 

8.9 
8.8 
10.7 
3.3 
9.0 

Lbs. 
2.50 
2.21 
0.41 
1.21 
1.33 
1.44 
1.04 

6.93 
5.41 
2.13 
1.80 
8.57 
3  00 
2.59 
7.68 
2.05 

1.09 
0.63 
0.37 

0.37 
0.14 
0.45 
0.22 

8.37 
6.79 
4.53 
8.36 
8.12 
8.90 

3.81 
35.15 
19.95 
21.56 

27.53 
29.26 
12.36 
11.35 
10,21 

Lbs. 
11.20 
14.82 
12.08 
14.57 
15.63 
14.11 
21.22 

37.33 
38.15 
32.34 
33.16 
:s8.40 
51.67 
33.35 
38.72 
43.72 

38.64 
40.58 
36.30 

7.83 
5.65 
16.43 
6.46 

64.83 
66.12 
60.06 
48.34 
69.73 
69.21 

9.37 
16.52 
54.22 
43.02 

32.81 
38.72 
43.50 
52.40 
41.23 

Lbs. 
0.41 
0.69 
0.37 
0.88 
0.36 
0.44 
0.64 

1.38 
1.81 
1.15 
0.57 
1.51 
1.34 
1.67 
1.54 
1.43 

0.76 
0.38 
0.40 

0.22 
0.11 

10.80 
14.52 
11.02 
14.26 
13.14 
10.31 
17.80 

34.41 
34.73 
30.53 
26.53 
42.76 
44.03 
36  97 
38.65 
33.56 

21.21 
20.87 
16.56 

7.82 
4.62 
18.05 
5.74 

80.75 
88.84 
72  05 
66.27 
81.72 
82.63 

14.82 
84.20 
79.32 
85.46 

78.92 
74.67 
46.33 
56.65 
48.23 

Clover  —  Red 

Corn  Fodder  

"     Silage  

Hungarian  Grass  

Rve.. 

Timothy 

Hav  and  Dry  Coarse  Fodders: 
AlfalfaHav 

Clover  Hay—  Red  

Corn  Fodder  (field  cured)  

"     Stover 

Cow  Pea  Hav 

Hungarian  Hay 

Oat   Hay.   .. 

Soy  Bean  Hav  

Timothy  Hay" 

Straws: 
Oat  

Rye  

Wheat  

Roots,  etc.: 
Carrots  

Mangel-  wurzels..  . 

Potatoes  

Turnips  

0.11 

1.60 
4.97 
2.94 
4.18 
1.36 
1.68 

1.38 
12.58 
5.35 
11.87 

7.06 
2.90 
1.16 
1.79 
2.87 

Grains: 
Barley  

Corn  

Corn  and  Cob  Meal..  . 

Oat  

Rye  

Wheat  

By  Products: 
Brewers'  Grains—  wet  

Cottonseed  meal  

Gluten  Feed—  drv  

"      Meal,  Buffalo  

Linseed  meal: 
Old  Process  

New      "     

Malt  Sprouts  

Rve  Bran  

Wheat  Bran  

Appendix. 


323 


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324: 


Agricultural  Chemistry. 


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325 


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INDEX 


Abomasum,  220. 
Acid,  definition  of,  16. 
Acids,  organic  in  plants,  99. 
Adult  animal,  253. 
Aerobic  organisms,  128. 
Albumin,  definiton  of,  100. 

in  plants,  101. 

in  animals,  207. 

in  milk,  271. 
Albuminoids,  definition  of,  207. 

in  animals,  207. 
Alinit,  60. 
Alkali,  "black,"  76. 

tolerance  of  plant  to,  77. 

"white,"  76. 

Aluminum  in  plants,  108. 
Alkaloids,  103. 
Amides,  in  plants,  102. 

in  animals,  208. 
Amines,  in  plants,  103. 
Amino-acids,  in  plants,  102. 

in  animals,  208. 
Ammonia,  in  the  air,  31. 

in  water,  32. 

loss  from  manure,  127. 
Ammonium  sulphate,  149. 
Amylopsin,  223. 
Anaerobic  organisms,  128. 
Animal,  constituents,  206. 

manure,  112. 

action  on  soil,  42. 

composition  of  bodies,  209. 


Antiseptics,  310. 

in  milk,  279. 

Ants,  in  soil  formation,  43. 
Apples,  195. 
Apatite,  38. 
Argon,  30. 

Armsby's  feeding  standards,  242. 
Arsenic,  as  insecticide,  294. 
Artificial  manures,  146. 
Ash,  in  animal  products,  210. 

in  feeds,  103,  218. 

importance  to  animals,  218. 
Assimilation  of  carbon  dioxide,  86. 
Ass's  milk,  278. 
Atmosphere,  23. 

Available  phosphoric  acid  in  fer- 
tilizers, 155. 

energy,  237. 
Avenin,  258. 
Ayrshire  milk,  270,  280. 

Bacteria,  action  in  digestion,  224. 

action  in  milk,  278. 

assimilation  of  nitrogen,  30. 
Barium,  in  plants,  109. 
Barley,  grain  composition,  183. 

straw  composition,  184. 
Base,  definition  of,  16. 
Basic  slag,  157. 
Beans,  grain    composition,  187. 

field,  187. 

soy,  187. 


328 


Agricultural  Chemistry. 


Beets,  194. 

Bile,  223. 

Bleaching  powders,  311. 

Blood,  211. 

dried  for  manure,  150. 
Boiler  scale,  71. 
Bone  ash,  156. 
Bones,  156,  212. 
Boracic  acid,  279. 
Bordeaux  mixture,  307. 
Bran,  wheat,  181, 
Bran,  corn,  186. 
Brewer's  grains,  184. 
Buckwheat,  189. 
Butter,  283. 
Butter  milk,  285. 


Cabbage,  196. 

Calcium,  function  in  plants,  106. 

occurrence,  12. 

carbonate,  37. 

in  soils,  38. 

cyanamide,  150. 

nitrate,  150. 
Caliche,  149. 
Calf,  composition,  210. 
Calorie,  definition,  8. 
Cane  sugar,  90. 
Capillarity,  53. 
Carbohydrates,  in  plants,  89. 

in  animals,  208. 

function  in  animals,  217. 
Carbolic  acid,  311. 
Carbon,  occurrence,  9. 

dioxide  in  air,  30. 

assimilation,  86. 

in  decay,  47. 

respiratory,  226. 

in  soil  gases,  60. 

as  a  solvent,  43. 
Carbon  disulphide,  307. 


Carcase,  composition  of,  209. 

in  increase,  211. 
Cartilage,  214. 
Casein,  271. 
Castor  bean,  189. 

oil,  189. 
Cellulose,  93. 
Cereals,  173. 
Chalk,  38. 
Cheese,  288. 

Chemical  changes  in  soil,  55. 
Chemical  manures,  147. 
Chili  saltpeter,  149. 
Chlorine,  bleaching  action,  15. 

as  a  disinfectant,  311. 

function  in  plants,  108. 

occurrence,  14. 
Chlorophyll,  86. 
Churning,  283. 

Clay,  occurrence  and  composition, 
45. 

physical  and  chemical  proper- 
ties, 48. 

Climate,  influence  on  plants,  200. 
Clovers,  191. 
Collagen,  214. 
Colloids,  53. 
Colostrum,  249. 
Cooking  fcod,  232. 
Combustion,  spontaneous,  96. 
Condensed  milk,  286. 
Connecting  tissue,  214. 
Constituents  of  plants,  22. 
Copper  sulphate,  309. 
Corn,  composition,  185. 

stover,  139. 

silage,  192. 
Cotton  seed  meal,  151,  188. 

oil,  188. 
Cow,  digestion  in,  220. 

ration  for,  263. 
Cream,  280. 


Index. 


32  D 


Creosote,  312. 
Creatin,  227. 
Creatinin,  227. 
Cresol,  312. 
Crops,  classification,  173. 

residues,   180. 
Crude  fiber  of  feeds,  174. 


Dairy,  267. 
Denitrification,  59. 
Dent  corn,  185. 
Dextrine,  93. 
Dextrose,  89. 
Diastase,  80. 
Diffusion  in  soils,  52. 
Digestibility  of  feeds,  231. 
Digestion,  218. 

coefficient  of,  129. 

energy  consumed  in,  237. 
Dips,  312. 
Disinfectants,  310. 
Dissolved  bones,  156. 

phosphate  rock,  154. 
Dolomite,  37. 
Drainage,  63. 


Eggs,  210. 

Elastin,  214. 

Elements,  7. 

Elimination  from  animal,  227. 

Energy,  lost  in  digestion,  238. 

utilized  in  labor,  255. 
Ensilage,  192. 
Enzymes,    79,    219. 
Ether  extract  of  foods,  175,  236. 
Evaporation,  from  plants,  85. 

soil,  54. 

Ewe's  milk,  249. 
Excretion,  in  animals,  227. 

in  plants,  83. 


Fallow,  54. 

Farmyard  manure,  112. 

composition,  113. 

decomposition  of,  122. 

preservation  of,  129. 
Fat,  digestion  of,  223. 

heat  producing  value  of,  216. 

in  animal  body,  213. 

in  feeds,  95. 

of  milk,  269. 

Fat  globules  in  milk,  270. 
Fats,  nature  of,  96. 
Fatty  acids,  saturated,  96. 

unsaturated,  96. 
Fat  production,  from  proteins,  265. 

from  carbohydrates,  265. 

starch  equivalent,  240. 
Fattening  animals,  258. 

rations,  259. 
Feathers,  206. 
Feeding  standards,  229. 
Feldspar,  36. 
Fermentation,   of   manure,   127. 

in  silo,  193. 
Fertilizers,  146. 

laws,  171. 

selection  of,  165. 
Flax,  188. 
Flowers,  87. 
Fluorine,  206. 
Fodder  crops,  190. 
Food  constituents,  function  of,  215. 

composition,   174. 

digestibility,  231. 

economy  of,  264. 

influence  on  butter,  275. 

influence  on  milk,  275. 

manurial  value,  115. 

production  value,  239. 
Formaldehyde,  310. 
Frost,  action  of,  41. 
Fruits,  195. 


330 


Agricultural  Chemistry. 


Fuel  value,  animal  products,  8. 

food  constituents,  237. 
Fumigation,  306. 

tobacco,  306. 
Fungi,  307. 
Fungicides,  307. 

Galactase,  289. 

Galactans,  93. 

Galactose,  90. 

Gases,  in  soil,  60. 

Gastric  juice,  220. 

Germination,  of  seeds,  79. 

Glaciers,  action  of,  39. 

Globulins,  100. 

Glucose,  89. 

Glutamin,  102. 

Glycerine,  95. 

Glycogen,  208. 

Goats,  digestion  in,  231. 

Grapes,  77. 

Grasses,  composition,  190. 

digestibility,  231. 
Green  manuring,  143. 
Gravel,  53. 
Grits,  38. 
Guano,  bat,  157. 

fish,  157. 
Gypsum,  162. 

Haemoglobin,  212. 
Hair,  152. 

Hardness,  of  water,  71. 
Hay  crop,  190. 

composition,  191. 

digestibility  of,  197. 
Heat,  of  animal,  254. 

of  combustion,  8. 

relation  to  plant,  87. 

relation  to  soil,  48. 
Hellebore,  302. 
Hemp  seed,  189. 


Hoof  meal,  152. 
Horn  meal,  152. 
Horse,  digestion  in,  220. 

labor  ration,  255. 

manure,  113. 
Humus,  function  in  soil,  46. 

physical  properties,  48. 
Hydrated  silicates,  37. 
Hydrates  of  iron  and  aluminum, 

37. 

Hydrocyanic  acid,  306. 
Hydrogen,  occurrence,  9. 

Igneous  rocks,  35. 

Increase,  while  fattening,  211. 

Indian  corn,  185. 

Insecticides,  294. 

Iron,  function  in  plant,  107. 

in  soils,  36. 

occurrence,  14. 
Irrigation  waters,  76. 

Jersey  mUk,   270,  280. 

Kainit,  159. 
Keratin,  207. 

Labor  ration,  255. 

Labradorite,  36. 

Lactic  acid,  in  milk,  278. 

in  silage,  193. 
Lactose,  271. 
Lead,  action  of  water  on,  72. 

arsenate,  300. 
Leaves,  function  of,  87. 
Leather,  152. 
Lecithin,  97. 
Leguminous  crops,  191. 
Leucine,  102. 
Lentils,  260. 

Light,  action  on  plants,  86. 
Lignin,  93. 


Index. 


331 


Lime,  as  a  manure,  161. 

in  foods,  266. 

in  soil,  38. 
Limestone,  46. 
Linseed,  188. 
Lipase,  80,  223. 
Litter,  118. 
Loco-weed,  109. 
London  purple,  298. 
Lupines,  144. 
Lysol,  312. 

Magnesium,   functions  of,  106. 

occurrence,  14. 

silicates,  37. 

Maintenance  ration,  253. 
Maltose,  90. 
Malt,  183. 
Maltsprouts,  183. 
Mangolds,  194. 
Manure,  farmyard,  112. 

application,  134. 

composition,  113. 

decomposition,  127. 

yield  by  animals,  114. 
Manurial  value  of  feeds,  115. 
Maple  sap,  90. 
Marl,  45. 

Marrow  of  bones,  212. 
Margarine,  285. 
Meadow  hay,  191. 
Metamorphic  rocks,  35. 
Methane,  production  in  digestion, 

238. 

Mica,  36. 
Milk,  albumin,  271. 

ash,  272. 

cows,  274. 

composition  of,  273. 

fat  of,  269. 

physical  properties,  273. 

powders,  286. 


preservation,  278. 

souring,  278. 

sugar,  271. 

of  various  animals,  268. 
Milking  cows,  rations  for,  263. 
Mineral  phosphates,  153. 
Minerals,  36. 

Miscellaneous  materials,  313. 
Muscular  tissue,  213. 
Muriate  of  potash,  159. 

Nitrate,  of  potash,  149. 

of  soda,  149. 
Nitrates,    conservation    of,    128. 

loss  by  drainage,  66. 

produced  in  soil,  57. 
Nitric  acid,  in  air,  31. 

in  rain,  32. 
Nitrification,  57. 
Nitro-bacter,  29. 
Nitrogen,  in  air,  27. 

assimilation,  27. 

fixation,  27. 

occurrence,  10. 

stored  up,  by  animals,  207. 
by  plants,  205. 

voided  by  animals,  216. 
Nodules  on  legumes,  45. 
Nucleins,  100. 
Nucleic  acid,  100. 
Nutrition,  of  animals,  214. 

of  plants,  18. 
Nutritive  ratio,  234. 

Oat,  grain,  184. 

hay,  191. 

straw,  185. 
Oil  meal,  189. 
Oils,  influence  on  milk  fat,  276. 

drying  and  non-drying,  96. 

essential,  98. 

nature  of,  98. 


332 


Agricultural  Chemistry. 


Oleic  acid,  96. 

Olein,  96. 

Oleomargarine,  285. 

Omasum,  220. 

Organic  acids  in  plants,  99. 

Oxidation,  16. 

slow,  96. 
Oxen,  ration  for  fattening,  258. 

ash  stored  up,  116. 

comparison  with  cow,  264. 
Oxygen,  in  the  air,  29. 

occurrence,  7. 
Ozone,  31. 

Palmitin,  96. 
Pancreatic  juice,  223. 
Pace,    influence   on    food    require- 
ment, 256. 
Pasteurizing,  279. 
Paris  green,  295. 
Pears,  195. 
Peas,  188. 
Peat,  118. 
Pectins,  94. 
Pentosans,  94. 
Pentoses,  94. 
Pepsin,  222. 
Peptones,  207. 
Perspiration,  227. 
Petroleum  emulsion,  305. 
Phosphates,  loss  by  drainage,  66. 
Phosphatic  fertilizers,  153. 
Phosphorus,    function    in    plants, 
107. 

occurrence,  12. 

in  animals,  210. 

in  foods,  218. 
Phytin,  110. 
Pigs,  ration  for  fattening,  260. 

rations  for  growing,  248. 

manure  of,  113. 


Plants,  assimilation,  86. 

constituents,  88. 

respiration,  87. 
Plums,  195. 
Pop  corn,  186. 
Potash,  loss  in  drainage,  66. 

fertilizers,  158. 
Potassium,  function  in  plants,  106 

occurrence,  13. 
Potassium  nitrate,  149. 
Potatoes,  195. 
Preservation  of  milk,  278. 
"Process"  butter,  284. 
Proteins,  classification,  100. 

kinds  of,  101. 
Ptyalin,  219. 
Putrefaction,  17. 

Quartz,  36. 

Quick  lime,  161. 

Raffinose,  91. 

Rain  water,  69. 

Rape,  189. 

Rechnagel's  phenomenon,  273. 

Reduction,  16. 

Reverted  phosphates,  154. 

Rennin,  221. 

Rennet,  288. 

Renovated  butter,  284. 

Resin  soap,  as  insecticide,  306. 

Respiration,  in  animals,  226. 

in  plants,  87. 
Reticulum,  220. 
Rice,  186. 
Ripening,  of  cheese,   289. 

cream,  284. 
River  water,  69. 
Rocks,  classification  of,  35. 
Root,  crops,  193. 

pressure,  83. 


Index. 


333 


Rotation  of  crops,  203. 
Ruminants,  digestion  by,  231. 
Rye,  182. 

Salicylic  acid,   279. 
Saliva,  219. 
Salt,  common,  163. 
Sand,  properties  of,  45. 
Schweinfurth's    green,    295. 
Sea  water,  77. 

Season,  influence  on  plant  compo- 
sition, 198. 

Seeds,  germination,  79. 
Sedimentary  rocks,  35. 
Separated  milk,  282. 
Sewage  as  manure,  75. 
Shales,  38. 
Sheep,  nutritive  ratio  for,  262. 

digestion  of  foods,  231. 

manure,  113. 

production  of  wool,  261. 
Silage,  corn,  192. 

clover,  192. 
Silicon,  function  in  plants,  108. 

occurrence,  15. 
Silicates  in  soil,  37. 
Size  of  animal,  influence  on  ration, 

254. 

Skimmed  milk,  282. 
Soap,  action  on  hard  water,  70. 

nature  of,  97. 
Sodium,  occurrence,  13. 
Softening  of  hard  water,  71. 
Soils,  composition  of,  61. 

definition  of,  ,35. 

fixation  of  nitrogen  in,  44. 

formation,  40. 

gases  in,  60. 

retention  by,  55. 
Soil,  sedentary  and  transported,  39. 

relation  to  heat,  48. 

relation  to  water,  52. 


tenacity  of,  50. 

water  in,  50. 

weight  per  acre,  61. 
Sorghum,  191. 
Specific  heat,  48. 
Spontaneous  combustion,  96. 
Starch,  in  plants,  91. 

influence  on  digestion,  233. 

part  in  nutrition,  217. 

productive  value,  240. 
Steapsin,  223. 
Stems  of  plants,  83. 
Stearin,  96. 
Sterilization,  279. 
Stomata  of  plants,  85. 
Stomach,  digestion  in,  220. 
Straw  as  litter,  118. 

energy  consumed  in  digestion 

of,  240. 
Sucrose,  90. 
Sugar  beets,  194. 
Sugars,  90. 
Suint,  262. 

Sulphate  of  ammonia,  149. 
Sulphur,  function  in  plants,  107. 

occurrence,  11. 
Sulphur  and  lime  wash,  302. 

dioxide,  34. 
Sunflower,  190. 
Super-phosphates,    154. 
Swede/crop,  194. 
Sweet  corn,  202. 

Temperature  of  soils,  50. 

Terpenes,  98. 

Therms,  237. 

Thomas  slag,  157. 

Tillage,  63. 

Timber,  composition  of,  179. 

Tobacco,  196. 

Transpiration  from  leaves,  81. 

Trees,  food  requirements,  195. 


3,34 


Agricultural  Chemistry. 


Trypsin,  223. 

Tubercles  on  legumes,  29. 

Turnips,  194. 

Urea,  227. 
Uric  acid,  227. 
Urine,  227. 

Vetches,  171,  205. 

Warp  soils,   76. 

Water,  action  of  on  lead,  72. 
action  of  on  rocks,  41. 
hard,  70. 
mineral,  69. 
natural,  68. 
organic  matter  in,  73. 
physical  properties  of,  68. 
rain,  69. 
soft,  71. 
spring,  69. 
typical  good  and  bad,  74. 


Waxes,  98. 

Wheat,  181. 

Wheat  bran,  181. 

Wheat  straw,  182. 

Whey,  291. 

White  ants,  43. 

Wind,  action  on  rocks,  42. 

Wolff's  feeding  standards,  235. 

Wood  ashes,  160. 

Wool,  production,  261. 

Woolen  waste,  152. 

Work,  production  of,  255. 

Worms,  in  soil  formation,  42. 

Xanthin,  213. 

Yolk,  of  wool,  262. 

Young  animals,  nutrition  of,  248. 

Zein,  101. 

Zinc,  in  plants,  109. 


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